Thomas Sutcliffe: Channel 4 is in decline, so it needs more than a safe pair of hands

'Jackson believed that public-service TV is moribund, Thompson thinks it simply needs healing'

Before anyone gets too hoity-toity about these matters, it's worth remembering that everyone wants to serve the public – even the most mercenary television executive in the world. They might want to serve that public a diet of televisual junk food, calculated to deliver the highest possible profit margin, but the idea of an audience out there eager to receive what they dispense is inseparable from the enterprise of broadcasting.

And even high-minded detractors of the old-fashioned concept of public-service broadcasting – Michael Jackson, for instance, who read its obloquys in his New Statesman lecture a few weeks ago – find themselves dependent on that convenient shorthand for the general appetite. Praising Channel 4's financial results last year (he would have a much harder job this one) he boasted that his channel had "broken through the mundane and formulaic nature of most modern television to capture the public's imagination".

Public service of a kind then – even if Big Brother and Ali G would not be quite what the old Reithian die-hards had in mind. The real question, it turns out, is less what you mean by service than exactly what you mean by a public. And for Channel 4 recently that definition has sometimes appeared pretty narrow. Older than 16 and under 25? Got a taste for salacious candour? You'll do nicely.

Mark Thompson, who was formally unveiled as Jackson's successor yesterday, will no doubt already be thinking hard about how to refigure the channel's definition of its public to more representative proportions. Over recent years he's appeared to play a curriculum vitae version of grandmother's footsteps with Mr Jackson, succeeding him as controller of BBC 2 and director of programmes at the BBC, and now trailing him into the main office at Horseferry Road.

But it's here that their footsteps are set to diverge. Where Michael Jackson was always restless in pursuit of novelty, an advocate of permanent revolution, Thompson has his eyes on an establishment prize – director general of the BBC. His arrival yesterday was greeted by many inside the building as the laying on of a safe pair of hands – an echo of the immediate reaction from Jeremy Isaacs, a man with a beady-eye for the butter-fingered. Where Jackson believed that the notion of public-service broadcasting was moribund, Thompson believes that it simply needs some sympathetic healing.

He has some basic first aid to administer first, though, before he moves on to the cosmetic surgery. For one thing, Channel 4's recent attempts to expand its franchise onto cable, with E4 and Film Four, are losing money steadily. For another, it's widely felt that the channel's schedules are in a somewhat dilapidated state. At the BBC Thompson enhanced his reputation by the clarity with which he tackled the main channel's structural problems – extending EastEnders and moving the news to 10pm. Channel 4 clearly needs the same kind of remedial architecture – Brookside, once a pillar of the channel's evening schedules, is in trouble, Richard and Judy appears to be a failed graft, and The Big Breakfast still needs replacing.

And if Thompson is to plant public-service values in this commercial soil, he will have to brace himself for the shock of a very different financial culture. BBC executives are insulated by the licence fee from the immediate consequences of their right to fail – but, as Michael Jackson learnt before him, a daily reminder that programme decisions have economic consequences is part of the lot of Channel 4's chief executive. Right now the messages are not all cheerful. Last month, for example, something like 70 per cent of Channel 4's advertising revenue came from youth-orientated advertising, a figure that inevitably must feed back into decisions about what to commission next.

There are silver linings, its true; the channel's surprising success with history programming, which recruits an older and highly desirable demographic, suggests that there is an open door for anyone wanting to bolster Channel 4's more serious output. Thompson, under whose watch Simon Schama's History of Britain series was commissioned at BBC 2, was believed to have been sceptical about the programme's potential, but he's not one to let a lesson go unlearnt.

He will have an intellectual ally at Channel 4 too – in the form of Tim Gardam, the director of programmes. Here too, though, there is much speculation about how well the alliance will hold together in practice. Both men are remarkably similar in background and intellectual approach, both spiritually serious and self-consciously academic – "I thought, Christ, two vicars at the top, what are we going to do," said one Channel 4 editor yesterday. But both men also have previous, as they say, having clashed when in rival positions at the BBC – when Thompson was running Panorama and Gardam was heading up Newsnight.

Thompson is known to be an adept navigator through complex political structures but he is now moving from a culture where the organisational flow chart looks like an unusually tidy Jackson Pollock, to one where it consists of a single fat black arrow. This points to Tim Gardam – and if Thompson is to loosen up the creative energies of his commissioning editors – currently a bit frustrated by the highly centralised organisation – something less directional will have to replace it. Channel 4 has always been a curious hybrid of high-mindedness and commerce – one that could have arisen in no country except one where publicly funded broadcasting competed hard with commercial broadcasting. But in recent years its statutory commitment to innovation has not always been elevating. If your goal is to remain always ahead of the mainstream – as Michael Jackson's was – it is all too easy to find yourself beating others to the low ground.

Mark Thompson at least has a less relativistic map in mind for the channel's future – one that incorporates the duty to walk against the flow now and then. When he joined BBC 2 there were those who feared that a "safe pair of hands" meant staid and grey, and he proved them wrong. If he does the same at Channel 4, then the whole public – not just those segments of it that the advertisers lust after – will have been well served.

t.sutcliffe@independent.co.uk