Slaughter and May and Linklaters have topped the league tables of the firms with the biggest shares of the listed company market over the last 10 years.

Published by Adviser Rankings, in association with audit and advisory firm Crowe Clark Whitehill and Wragge Lawrence Graham & Co, the rankings place Slaughters at the top of the table for the total number of stockmarket clients.

The firm has seen only a minimal change in the number of listed clients on its books since 2005 when it advised 118. The latest figures, published today, show that the firm currently advises 111.

Linklaters has also retained its 2005 top place in the rankings, advising clients with the largest total market capitalisation. In 2005 the firm advised clients with a combined market capitalisation of £582bn while the latest figures list the combined value of the firm's clients as £778bn.

Long term thinking
Andy Ryde, head of Slaughters' corporate practice, says the firm's "long term view" and its "relationship driven, not product driven" ethos was why it had remained at the top of the league table.

"We know that if we build a long term relationship with a client that over time that relationship will be productive. All our corporate lawyers are multi-specialist, so we can always act on whatever our client is doing – whether that's a public M&A public takeover, cross border M&A work or capital raisings."

Ryde also said that the way the firm handled the financial crisis was key to its success over the last ten years.

He said: "The financial crisis was a test for law firms as we had to be very sympathetic to clients who had internal cost pressures. During those years, when there were leaner fees and less M&A, we worked hard at staying in touch with clients. They still needed to be supported.

"I think that's why we've had such long term success with our clients, because we kept the relationships going even when there was a lack of big M&A work. In some ways it actually helped, because companies would draw on a fuller range of our offerings, such as litigation and competition lawyers. That built up a deeper and wider relationship."

Some of the major clients Slaughters kept hold of over the ten years include housebuilder Barratt Developments, JP Morgan and drinks giant Diageo.

Movers and shakers
Major movers over the decade include Herbert Smith Freehills, which has jumped up seven places in the total stockmarket clients table over the decade, moving from ninth place in 2005 to third place in 2015. During that time the firm has raised its total FTSE 100 clients by eight to its books.

Among the clients the firm has picked up over the ten years are Easyjet, security company G4S and engineer Weir Group.

Meanwhile Ashurst has fallen from second place for total stockmarket clients in 2005 to 11th place in 2015 as the number of clients on its books fell from 116 to 71.

Simon Beddow, global co-head of the firm's corporate, competition and tax division, said that the firm had made "a concerted effort to improve the quality" of its clients over the decade and therefore it was surprising the firm still had a high number compared with some other firms.

We no longer act for quite a lot of the small public companies we acted for a decade ago

He added: "We no longer act for quite a lot of the small public companies we acted for a decade ago, because it wouldn't have made sense to. Some of those companies have disappeared, or gone to smaller law firms."

Beddow said that price pressure meant that firms had to "fight harder to keep a decent share of the market".

He added: "I think that as a result of price pressures, the magic circle firms have focused a lot more intensely on FTSE 250 companies, rather than just the top end of the market. They've broadened their hunting ground."

Taking AIM
On the AIM market Wragge Lawrence Graham & Co topped both rankings for number of clients and the total market capitalisation of its clients.

In 2015 the firm had 60 AIM clients on its books with a total market cap of £6.05bn. Pinsent Masons and DLA Piper also ranked highly in the AIM league tables. Pinsents ranked second for the number of clients with 59. Its clients had a combined market capitalisation of just under £4bn putting third in that league table.

DLA Piper had the fifth biggest book of clients at 38 and the second highest total market capitalisation with £6.01bn.