BIS head of legal Rachel Sandby-Thomas quit a promising City career to become one of Whitehall's top lawyers. She speaks to Alex Aldridge about life in government

The public sector is enjoying a spell of popularity – both among out-of-work City lawyers looking for jobs and partners hoping to drum up business from a sector still with some money to spend.

"Recently I've found myself having a lot of conversations with law firms that have suddenly become interested in public sector work," smiles Department for Business, Innovation and Skills (BIS) head of legal Rachel Sandby-Thomas.

She says that the secret to impressing during one of these discussions is demonstrating a knowledge of the workings of the recently re-branded BIS – previously known as Department for Business, Enterprise & Regulatory Reform (BERR) until last month's merger with the Department for Innovation, Universities and Skills (DIUS), and before that as the Department of Trade and Industry (DTI).

"What we're not looking for," continues Sandby-Thomas, "is assistance on things we have a specialism in like state aid – yet I've lost count of the number of state aid presentations I've sat through from firms."

Winning business from BIS requires a long-term view, with the vast majority of legal work generated by the department going to firms on the Government Legal Services (GLS) panel, which is not up for review until 2011. The panel, which serves all of the GLS's 30 departments, is broken down into eight different sections and contains a total of 52 law firms, among them several leading City outfits including Allen & Overy, Freshfields Bruckhaus Deringer and Norton Rose.

Belfast-born Sandby-Thomas is used to dealing with City lawyers, having trained with Linklaters and gone on to spend two years in the firm's commercial litigation team. But she never quite saw herself as one of them.

"I went to Linklaters basically because I thought it would give me gold-card credentials – and it did. But even before I started, deep down I knew it wasn't for me," she reflects. "And it was sometimes quite difficult having a bubbly personality there."

A move to the GLS was not part of the long-term plan, though – indeed it came about by "complete happenstance" when Sandby-Thomas sneaked down to the Linklaters library one Tuesday in 1992 and stumbled over a newspaper advert for the GLS.

"I'd no idea the Government even had lawyers at that point, but the job sounded interesting – like being a barrister without the advocacy – so I put in an application," she recalls.

After successfully negotiating the gruelling interview process – during which candidates are grilled on a legal problem by three senior government lawyers – Sandby-Thomas said farewell to the City and began life as a lawyer in one of the advisory teams to the Treasury Solicitor's Department. Two-and-a-half years later she moved to the Cabinet Office, where she spent another couple of years, eventually arriving at BIS via spells in the Attorney General's Office, the Department of Health and HM Revenue and Customs.

Her role at BIS, which sees Sandby-Thomas head a team of more than 100 lawyers, requires a mixture of legal and management skills. For both, Sandby-Thomas says that she draws heavily on instinct.

"With law I'll often use instinct as a guide. So if something doesn't appear right, I'll shake it and work backwards, pulling the issues apart to get to the nub of the problem," she says, adding that her management style is about "following her gut feeling about people, then empowering and trusting them unless there is a strong reason not to".

BIS's legal team is split into two divisions: enforcement and advisory – the former specialises in investigating and prosecuting infringements of the Companies Act and the UK Insolvency Regime; the latter advises on the legal aspects of new policy. At times the remits of BIS and the Financial Services Authority (FSA) overlap – for example, insider trading prosecutions used to be handled by BIS predecessor the DTI before they were transferred to the FSA in 2001 – but the basic division is clear: "We regulate companies, they regulate financial services," says Sandby-Thomas.

Recent highlights for the department include handling the competition law and state aid elements of the recent 'Real Help for Business' initiative and the Digital Economy Bill, of which a preliminary report was published last month. But it was the January merger of HBOS and Lloyds that really stands out for Sandby-Thomas: "Being asked to advise on the competition aspects of the proposed merger in an already fast-moving environment was the trickiest thing I have ever had to do. And it was brilliant to have a little part in what was huge at the time," she recalls.

One of the ways Sandby-Thomas handles the pressure of being responsible for high-profile work is by abandoning London every evening in favour of "deepest, darkest West Sussex", where she lives with her husband and two children. But when the pressure is on in Westminster, you get the impression that the laid-back BIS legal chief doesn't have too many problems holding herself together. What's her strategy for keeping calm?

"I focus on not panicking, because panicking denotes knowing what you should do but not being able to do it," she responds. "Of course, there are times when I don't know what I should do because it is so new, but then I console myself with the thought that I'm not even at the panic stage, and kind of go from there."