Gordon's new broom needs bold brushwork to fix No10

The shock was that Gordon Brown clearly felt the need to have someone in such a key post. It was an indication of just how far matters had sunk under Brown that now, six months after he first entered No10, that he was giving in and saying he needed help. Plagued by a lack of focus and hesitancy, the Prime Minister hopes Carter will provide clarity and organisation.

While Carter is little known in politics, the fact he was chief executive of Brunswick, the leading City public relations agency, and before that the founding chairman of Ofcom, the communications industry watchdog, were credentials enough. He was immediately billed as a spin-doctor, one with experience of regulation and Whitehall, parachuted in to save Gordon.

As ever, though, where politics and PR are concerned, everything is not what it seems. For a start, Carter, 43, though CEO of Brunswick, is not a seasoned PR man. Neither is he anything approaching the head of the agency he is leaving.

Brunswick was founded in 1987 by Alan Parker, son of Sir Peter Parker, the former railways boss, and a consummate communicator. Ever since, as the firm has grown to advise more than 25% of the FTSE 100 and opened offices around the world, Parker has kept a firm hand on the tiller. For most of that period, the equity in the agency was his. Recently he has relinquished some of the shares to incentivise senior staff, but the majority is still tightly in his grasp.

Within the agency, too, there is a pecking order. Immediately beneath Parker are his co-founders, Andrew Fenwick and Louise Charlton. Other figures with clout are those who bring in the business, who deal directly with clients. Carter, who only joined Brunswick early last year, was none of these.

Instead, his role was to shake up Brunswick, to put the place on a more efficient footing, to explore how to alter the structure in a way that meant Parker could remain in control but employees could be duly rewarded and discouraged from leaving.

Carter's arrival at Brunswick was a shock. He had been widely tipped to take over at ITV, then seeking a successor to Charles Allen. With hindsight, he was possibly too similar to Allen to pass muster. He wasn't a broadcaster with a string of hit shows to his name. Like Allen, he was a Scot, dry and sharp, occasionally abrasive.

He's charming enough but he isn't an easy person to know. It's like he's got a protective glaze to him - the result of slight nervousness and shyness and also perhaps of being short-sighted.

He's clever, an intellectual with depth, who is interested in theatre (like Parker, he is a governor of the Royal Shakespeare Company) and sport. He's a keen runner, fit and wiry. He lives in Barnes, in south-west London, in a large house with his wife and two children. He's also political - he was a left-leaning Labour activist in his youth.

Carter grew up in Edinburgh, went to university in Aberdeen where he studied law. Unexcited by the prospect of a life contemplating Scots law, the ambitious Carter came south, joining J Walter Thompson, the advertising agency, as a graduate trainee specialising in media and technology accounts. Eight years later, and before he was 30, he was in charge of the agency. From JWT he went on to run NTL, the floundering cable giant.

It was not a happy period. George Blumenthal, the cable operator's colourful co-founder, accused him of adding to its woes, not alleviating them. When Blumenthal left, he sent an email to staff lambasting "the management consultants, the toothpaste marketers and the other Carterets".

When it came, Carter's own going was sweetened with a pay-off and bonus worth £1.7 million - but not before NTL had filed for bankruptcy protection. His wunderkind image and slick presentational skills didn't go down well with investors who were left nursing substantial losses. "All fur coat and no knickers," was one uncharitable view of his stint at NTL.

But behind the scenes, say others close to the company at that time, Carter had an impossible task. They pay tribute to his tireless efforts to lift a deeply demoralised workforce.

He was able to shake off the NTL hangover by becoming the first chief of the new Ofcom regulator ( he resigned his Labour Party membership to avoid accusations of bias). It was a tough call - the body's remit was as broad as the office was large, employing some 1000 people from its glass temple overlooking the Thames at Southwark Bridge.

Carter gave Ofcom authority. Under his stewardship it soon became feared in telecoms, radio and TV - regarded as unpredictable and no pushover. He was resolutely independent, refusing to allow any suggestion of favouritism to stick to him or the watchdog. In an industry built upon favours and networking this made him something of an outsider - aloof and distant from the practitioners. While ITV was preferring-Michael Grade for executive chairman, Carter was in talks with Parker. When Carter made his move he said he was looking forward to returning to an agency and also privacy. What also attracted him was Parker's design for the firm.

Parker does not see Brunswick as just another PR outfit. He genuinely sees it as occupying a similar spot in public relations to McKinsey's in management consultancy - top of the tree, a respected, recognisable global brand. Carter's role was to help him get there.

Carter impressed his new colleagues by addressing them at a management away day soon after arriving. They couldn't avoid noticing that Parker was prepared to let him take the floor. But privately, the two men didn't always see eye to eye. Parker is a mercurial talent, not easily tied down. Always with him, clients come first. Carter complained of being frustrated.

Despite his proximity to some of the very grandest captains of industry, Parker is of the liberal left persuasion. Down the years he became close to the Chancellor. He visits him and his wife, Sarah, in their Fife home at weekends. He employed Sarah (she has since left Brunswick but they still work on charitable projects together) and they were guests at his second wedding. Gordon is godfather to Parker's young son William. The PR man's sister, Lucy, advises Brown on his presenting.

When Brown met Carter, he couldn't help but be impressed. Parker knew of Carter's political aspirations, even though Carter had said they were publicly on hold. When Brown said he wanted Carter to become his chief of staff and improve the running of No10, Parker did not demur.

It appealed to him that a Brunswick alumnus was taking such a significant post. This is something Parker holds dear. Part of McKinsey's reputation relies on old boys and girls holding down top jobs elsewhere. At Brunswick, Parker collects well-known names - Sarah Brown was one, James Rubin, a former Bill Clinton close aide, was another.

He's done well on the Tory side, too. Simon Walker, an ex-Brunswick partner, was a special advisor in the Prime Minister's Policy Unit from 1996 to 1997. MPs Greg Barker and Richard Bacon were at Brunswick.

Having Carter inside Number 10 is a feather in Parker's cap. It puts distance between Brunswick and the rest. And it keeps him in with someone who over time may have proved an irritant.

One FTSE 100 company marketing director who in the past worked closely with Carter says: "I reckon he sees himself as a future Cabinet minister, and this could be a stepping stone into politics. I think he'd go the MP route rather than try to finesse a way through the Lords. But perhaps a future Attorney General? He studied law, after all. He is a consummate politician and very talented too."

What Carter will also bring to Downing Street is speed. Former associates say he thinks quickly and acts immediately. He's a technocrat who loves to bury himself in the minutiae of a plan. He must shake-off a natural nerdy earnestness and be seen to be bold.

As an attender at Cabinet, his brief will be to identify where measures break down and how delivery can be accelerated. He won't take prisoners and he's unlikely to be popular. But it's not his mission to be universally liked.

It's a brave step. Carter is unversed in high-level government and has little time to complete the learning curve. Brown, however, may just have chosen well - with a little help from a friend.