Before I meet Siemens' new UK general counsel Claire Carless, I know only a handful of disparate things about her. She was formerly legal director at Vodafone and, before that, legal manager at National Power. She is a trustee of LawTrust and passionate about pro bono. She likes chocolate and red wine (together) and she has two teenage sons, a dog, five chickens and six pigs.

I am interviewing Carless at Siemens' UK headquarters, Sir William Siemens Square in Frimley, Surrey. Not until you've been there do you start to comprehend the size of the company – it employs 13,000 people across nearly 40 sites in the UK, and just less than 400,000 people worldwide.

"Do all of these buildings belong to Siemens?" I ask the taxi driver, as we arrive at the square. "You're new to this, then?" is his, I presume, rhetorical question.

I am early and the receptionist hands me a health and safety leaflet that – conforming to a number of stereotypes of a German engineering and technology company – gives me detailed instructions on what to do if asked to evacuate the building (do not take drinks, apparently), while telling me that effective health and safety is a cornerstone of Siemens' business.

The loo doors warn users to be careful when opening them, and I genuinely wonder what is behind until I realise this is just another precautionary sign.

Carless is late and deeply apologetic. I can't help wondering how she is finding this cultural shift away from the dress-down, slightly trendy telecoms culture I have witnessed first hand at Vodafone's London office (albeit she was based in its headquarters in Newbury, Berkshire).

Carless laughs when I ask, but reminds me that being fastidious about health and safety in a heavy engineering company is a matter of life and death.

However, within legal, she says the position is very different. Lawyers are not entitled to be cautious and sit on the fence, but are expected to be fully part of the business. Carless is only too aware that this is a bit of a cliched in-house mantra but at Siemens, she says, unlike some companies, it is paid more than lip service.

"Lawyers are not the decision makers," she says, "but they can't just say 'your options are this or that'. You are expected to say 'this is something you need to be aware of, but it's not actually all that important in this case and my vote would be to do it this way'."

Nor do you have to fight to be let into the boardroom. As part of the company's 'lean board policy' – which does what it says on the tin, including keeping the boards of Siemens' 40 or so holding companies as small as possible – each board will include the chief executive, the chief financial officer and the general counsel.

The structure of the legal department appears unusually complex to an outsider and I am slightly baffled by Carless' talk of vertical profit centres and regional reporting lines.

But in very basic terms, Siemens worldwide is divided into four key sectors: energy, health care, industry, and infrastructure and cities. The UK legal team reports to Carless and comprises 35 lawyers, 17 contract managers, six compliance officers, 11 support staff (many of which are part-time) and two company secretary assistants.

A return to the UK

This is the first UK-based job Carless has done since the 1980s, when she was at Stephenson Harwood in London. After a three-year stint in the City law firm's Hong Kong office, Carless moved in-house to newly privatised National Power in 1992, driven by the desire to move her young family out of the city yet fulfil an interesting corporate role.

The next eight years were spent travelling the globe negotiating power station contracts, culminating in the 2000 demerger of National Power's domestic and international business – Innogy and International Power. When Carless was offered the general counsel and company secretary role at International Power, she turned it down – because the job was based in London.

Carless used to joke that her perfect job would be to work for Vodafone, which was ten minutes down the road from her home in Newbury. Encouraged by a Linklaters partner to write to then general counsel Stephen Scott for a job, Carless recalls: "So I did. He said come in and let's talk and he gave me a job."

Eleven years later, she finally felt like she had reached the end of the road and couldn't see the next step. When the job at Siemens came up, she was attracted by the new challenge of a multi-sector business, the company's emphasis on renewables and regeneration projects, her first UK role and, of course, a promotion.

We have a refreshingly frank and slightly off-piste discussion about the way family pressures have influenced her career choices and the fact that her husband gave up work 11 years ago to raise their children.

The pressures of two people with high-level careers and nanny trouble meant "things started to crack". He has only just gone back to work part-time to fit around her sons' school holidays and, while Carless admits to feeling like she is missing out at times, the arrangement has worked well.

She also admits to thinking it is a myth that serious career women "can have it all".
I reluctantly get back on track to the nitty-gritty detail of deals, panel and legal spend. Siemens, led by in-house lawyer Nicola Jordan, is in the final stages of negotiating its £1.4bn Thameslink trains contract, despite calls by trade unions to award the deal to the Bombardier plant in Derby.

Pinsent Masons and Reed Smith are assisting on pensions and property issues respectively, and Linklaters is advising Siemens Project Ventures and other equity providers. But the lion's share of the deal is being handled in-house, which Carless says is "fantastic".

In common with most legal teams, Siemens is managing its headcount tightly and, while legal has not been asked to cut numbers or freeze headcount, neither is it really growing, despite the huge demand for legal services today.

Meanwhile, France's Alstom Transport has called off further legal action stemming from its claim that Eurostar unfairly handed Siemens a €600m (£484m) contract for a new fleet of trains. Freshfields Bruckhaus Deringer advised Siemens on the claim and Hogan Lovells acted for Alstom.

Exciting new projects

Carless reels off a raft of other new and ongoing UK projects and this heightened activity has pushed legal spend up to about £4m, from an annual average of between £3m and £4m.

The UK panel is up for a procurement-led review this summer or autumn, and Carless will be looking at what firms have been used for, whether they provide the right mix of expertise, whether the individuals are the right fit, and looking for "that horrible phrase 'value-add'".

The engineering firm's UK panel includes Pinsent Masons, Reed Smith, Manches and Hill Hofstetter, and Siemens recently added Addleshaw Goddard and Watson Farley Williams to advise on finance because "there was a gap". The firms in the Scotland panel are Biggart Baillie and Shepherd & Wedderburn, while Arthur Cox is the firm's adviser in Ireland. The number of firms is about right, and Carless does not expect to completely revamp the panel but she would be "surprised if there are no changes".

I'm conscious of the time, and we briefly discuss Carless' pro bono work and the fact that the Siemens' UK team are excited about shortly becoming members of LawWorks. But before I wrap up the interview I have to check: does she still have chickens and pigs (as I had learned from the LawWorks website)?

Carless laughs: "I have a habit of saying these things and then they are out there on the internet forever." In fact, she has two pigs, a dozen chickens, a dog, a goldfish, two teenage sons and, I have deduced, a very supportive husband. No wonder she also likes red wine and chocolate (together).