The British Empire may be long gone, but its legacy of common law legal systems in countries including Australia, New Zealand, India, Canada, Singapore, Hong Kong and South Africa is proving to be a real boon for London's leading law firms, for whom history has provided a large pool of well-qualified, experienced legal talent willing and able to relocate and hit the ground running in times of high demand.

This certainly is one of those times. The recovery of the London M&A market has coincided with a demographic depression in the available numbers of UK-qualified lawyers, thanks – in part – to the downturn in newly-qualified retention rates at the turn of the decade following the end of the dotcom boom.

As a result, UK law firm partners are not only pounding the streets of Sydney, Melbourne and Auckland but also those of Johannesburg, Cape Town, Toronto and Vancouver in their search for newly-qualified recruits – to the extent that one London-based recruitment consultant estimates that 80% of the magic circle's recruitment to their corporate and finance practices in the past year is accounted for by Commonwealth candidates. "They have not entirely given up on finding UK finance and corporate lawyers, but they are pretty close to it," he says.

Fortunately enough, they are finding a considerable number of willing candidates, drawn to London by its high salaries, international deals and clients, proximity to Continental Europe and its relative cultural similarity to home.

One of many London firms waiting to give them a warm welcome is Linklaters. "Recruiting within the UK and Irish markets is still important to us, but it is not large enough to satisfy our needs at qualified level," says Caroline Rawes, Linklaters' head of human resources. "Hiring the best lawyers is critical to our success as a firm and in any resourcing strategy, it is key to identify where the pockets of talent lie. If that corresponds with an interest from lawyers there in coming to work for us, then that is where we will focus our attention."

This is not the first time that London's law firms have turned to Commonwealth countries to fill the ranks, but the renewed recruitment drive does a have a few distinct features compared with the last time around during the late 1990s.

What has changed since then is the range of roles being made available to Commonwealth lawyers. In the 1990s, the majority of those recruited went into the highly leveraged corporate and finance departments, but more recently, recruitment has broadened into 'commercial' areas such as construction, property, IP and even employment law.

Law firms have also broadened the search from their former focus on Australia and New Zealand. There is some sense that both of these countries have been over-exploited to an extent, hence the search has been widened to include South Africa and, more recently, Canada, where Freshfields Bruckhaus Deringer and Herbert Smith have recently launched recruitment campaigns.

The advantage of hiring lawyers from any of these jurisdictions is the ease with which lawyers can be assimilated. "It does not take them long to get up to speed," says Tim Marsden, head of the corporate finance practice at Norton Rose, another firm that has been actively recruiting down under. "We recruit from very good firms in Australia and New Zealand where the law and culture is pretty similar."

A further advantage of many Commonwealth lawyers to UK firms is their greater willingness to be deployed to other parts of their international networks – to the extent that some UK-headquartered firms are specifically recruiting Commonwealth lawyers directly for their overseas offices.

Linklaters' London, Moscow and Asian offices, for example, are soon to launch a joint recruitment campaign in Australia and New Zealand, while the main focus of CMS Cameron McKenna's Commonwealth recruitment drive is its network of Central and Eastern European offices.

"We are actively looking at both the Australian and New Zealand markets, driven mainly by our growing offices in Central and Eastern Europe," says Camerons' senior people and development manager for Central and Eastern Europe, Rob Worrall. "Australia and New Zealand offer high quality candidates who are eager to work abroad."

The mobility and flexibility of many Commonwealth-educated lawyers is also leading to increasing levels of interest in recruiting common law-educated candidates at graduate level. Linklaters has a specific scheme to attract Australian graduates to train in London, in part also because the Australian universities' tradition of only offering law as part of a combined degree means that they often have a more rounded approach.

And while the small firm culture that has survived in Singapore and India due to their protected legal markets makes it harder for qualified lawyers from these jurisdictions to fit into UK firms at qualified level, prospective lawyers from these countries are in high demand at graduate level.

Linklaters is one of a number of UK law firms actively targeting Indian students. "They have a common law background, a thorough university course and the quality of students is very high," says the firm's graduate recruitment manager, Claire Cherrington.

The other change in the dynamics of Commonwealth recruitment is the increasing number of lawyers that stay with UK firms for the medium to long-term, whether in London or elsewhere in their networks. Employment is mostly offered to Commonwealth lawyers on the same terms as homegrown solicitors and a growing number no longer see it as just a short-term stint before returning home.

"There is an awareness among London firms that people may only be here to gain some international experience, but the proportion of people that stay for longer is increasing and there are growing numbers of Australian and New Zealand-qualified partners at magic circle firms," says Lynnsey McCall, a recruitment consultant in the London office of Taylor Root.

This accords with Linklaters' experience, says Rawes. "It is a myth that Australians and Kiwis only come over for a couple of years," she says. "A good proportion stay for the mid to long-term and we are looking for good people who can enhance and develop their careers with us. In our experience, many of our partners originally came over for two years and have stayed for five to 25 years. "We see that also with graduates. When we started the scheme in Australia, we had reservations that a lot of them would want to go back home when they had qualified, but we have been very encouraged by the fact that many of them are still here and doing very well, perhaps moving around the firm to continue their careers."

For many lawyers, the crunch time comes around five years after qualification. "Time spent in London is a brilliant experience, but the danger is leaving it too late to return home," says Tim Fogarty, an Australian legal recruiter based in London with Taylor Root. "There is an issue in Australia about recruiting returners that are too senior and promoting them above people that have stayed in Australia. It is generally better to spend two to three years in London and then have a couple of years' run-in to partnership back home. If you leave it later than five years' post-qualified experience (PQE) – in UK terms – then your options start to fall away."

For those Commonwealth lawyers who do return home in good time, the experience they gain will usually stand them in good stead when it comes to their future careers and partnership prospects. Law firms will generally give full post-qualification credit for time spent practising overseas and the one or two years' PQE lopped off when moving to the UK (due to the shorter training period in most Commonwealth countries) is added back when calculating salaries.

"International experience looks good; having worked in a magic circle firm indicates that you have had exposure to large and important transactions and is often an open invitation to work in the best firms in Australia and New Zealand," says Simon Swallow, recruitment consultant in the New Zealand offices of Global Career Link. "The fact that a lawyer has worked over-seas and 'got it out of their system' can mean that they are looked at as less of a 'flight risk' when they return.

But the biggest issue for returners is redeveloping the client base required to make it as partner."

The exception to this rule, it seems, is Canada, where time spent in London is less likely to elevate returning lawyers above their stay-at-home peers. "Personally, I think it is valuable experience for Canadian lawyers to work in London on multinational deals rather than just Canada-US transactions, but while law firms think it is a good thing to have on a CV, it is not necessarily a big advantage over someone who has spent their whole career in Canada," says Christopher Sweeney, president of Canadian legal recruitment consultants ZSA.

Yet while the benefits to Commonwealth law firms in acquiring returning lawyers with a few years' blue-chip experience under their belts are obvious, the cyclical brain drain to the UK also creates significant headaches. UK firms' recruitment efforts are heavily focused on the top-tier firms in each jurisdiction and the recruitment rush of the last couple of years has left Antipodean firms in particular with unevenly-shaped practices, with large numbers of junior and relatively senior lawyers, but a deficit of mid-level lawyers with two to six years' PQE. In the traditional law firm model, these are the most profitable lawyers, but in Australia and New Zealand especially, there are great big holes in the ranks.

In both countries, the annual exodus of mid-level lawyers is generally regarded as a fact of life and most firms acknowledge that it is futile to try to stem the flow. An increasing number of Australian law firms are attempting to turn the tide by mounting recruitment campaigns in London, aimed at both Australian and UK-qualified lawyers, while Australian firms are also looking to South Africa and Canada to replace lawyers bound for the UK. Some have established secondment relationships with UK firms or are offering unpaid career breaks so that their lawyers can get overseas experience without having to resign.

But the main strategy is to ensure that they remain on good terms and in contact with their alumni, either in the hope of getting them back in the future or by benefiting from close links to UK law firms if they stay abroad.

"Our alumni are very important to us," says Greg Eder, human resources director at top-tier New Zealand firm Simpson Grierson. "Heading overseas is part of the culture and we recognise that people will go, so our focus is on how we can maintain our connection while they are away because we want to ensure that we are the firm they choose to join when they return. When partners are visiting key cities such as London, New York or Sydney we will always look at connecting with our alumni while we are there."

Some leading Australian firms, such as Clayton Utz, have developed formal alumni programmes to achieve the same ends. "It makes sense to remain on good terms with those who go overseas, so that we can either have them back or they can help us by sending us work and spreading the word about us," says Geoff Simpson, head of Clayton Utz's Perth office.

In Canada, according to ZSA's Sweeney, the number of lawyers leaving for the UK is currently too low to create much concern at the country's leading firms. UK firms do not pay significantly more than Canadian practices and the main focus of the Canadian brain drain in the 1990s was towards US rather than UK firms. In South Africa, however, where the widespread overseas recruitment of lawyers is a more recent phenomenon, the subject remains a sore point with some law firms, which are only now coming to terms with the implications for their profitability and their recruitment and training of junior lawyers. Campaigns by London law firms have been running for two to three years, but activity has increased sharply this year and is gathering momentum as expatriates recommend former colleagues to their new employers.

"We do not like it much, but there are benefits if these people come back with good experience," says Chris Ewing, chairman of leading South African firm Cliffe Dekker. "We would rather that London firms did not do it, but we understand why they do."