John Reid is said to have "visibly gulped" when Tony Blair sat him down in his No 10 office and offered him the job of health secretary. This show of timidity in a man routinely described as a "bully", "bruiser" and "thug" reflects just how daunting the department of health has become.

A look back through history shows just how tough the job is. None of the four health secretaries of the last decade - Virginia Bottomley, Stephen Dorrell, Frank Dobson and Alan Milburn - have emerged from the department stronger political figures.

The new health secretary is a man with many contradictions. He is a former heavy smoker and reformed alcoholic who is now health secretary, a former communist who is now a loyal new labourite, a catholic unionist and finally a political bruiser and yet one of the sharpest minds in the cabinet. His father was a postman, his mother worked in a brewery and he left school at 16 before gaining a doctorate on the 19th-century West African slave trade and going on to become a Cabinet minister.

Now Mr Reid (he has stopped calling himself Dr since he became health secretary) is the man Tony Blair turns to when there is trouble. He started out in 1997 as a defence minister - the department he is most interested in. The prime minister quickly made him transport minister once it became clear that transport problems were damaging Labour. Following the resignation of Peter Mandelson (again) he became Northern Ireland secretary at a sensitive time in the peace process. He took over the role of party chairman in the reshuffle following the resignation of Estelle Morris and then became leader of the house when Robin Cook walked out over the Iraq war. After only 70 days in that job he has now been moved to health - his fourth cabinet job in a year.

Critics question whether he has stayed long enough anywhere to have made an impact. His lengthy CV does not inspire confidence that he will remain as health secretary for long enough to make much of a difference. However he could not have taken over health at a more important time for the government.

In August a Mori poll found that 43 per cent of people believed that the NHS and hospitals were the most important issues facing Britain today. The economy and the economic situation polled only nine per cent.

Mr Blair is well aware of the need, come the next election, to prove to a sceptical public that real improvements have been made for all the money spent. The prime minister told Jeremy Paxman back in February: "The problem that we have is this, and just let me try and explain it from where we sit for a moment. We are putting up people's taxes in April - which is a difficult thing to do in one sense - we're putting up people's tax in April to put more money into the Health Service. We have to be able to show real outcomes as a result of that."

Mr Reid will be expected to use his well honed media skills to convince the electorate that the NHS is indeed improving.He will also be expected to push through the reforms his predecessor started off. This will require standing up to two difficult opponents - Labour backbenchers and Gordon Brown.

Despite his reputation Mr Reid has so far sought to distance himself from the confrontational style of his predecessor and has struck a conciliatory tone with backbenchers.

He used his first speech as health secretary to declare that the 55-year-old goal of "equal access" to the NHS has yet to be realised. In a passage of the speech aimed at discontented Labour backbenchers he highlighted the fact that lower socio-economic groups have a 30 per cent higher need for hip replacements yet a 20 per cent lower rate of operations.

Despite Mr Reid's efforts a rebel amendment to wipe foundation hospitals entirely from the Health and Social Care Bill was defeated by 286 votes to 251 in early July. That left the government majority cut from 164 to 35 - its lowest since coming to power in 1997 - with 62 Labour MPs voting against the hospital plans.

The chancellor is an altogether different opponent. Mr Milburn won the admiration of No 10 by openly relishing his battles with Mr Brown. Mr Reid is in a good position to do the same. He was one of the first and certainly the most prominent of Scottish Labour figures to back Mr Blair in the leadership race following the death of John Smith in 1994. There is little love lost between the two of them and Mr Reid is unlikely to have much of a role in a future Gordon Brown government.

Another bit of unfinished business left by Mr Milburn was the dispute over consultant contracts. Again Mr Reid's negotiating skills - skills he proved in the subtle and dangerous area of Northern Ireland - were more in evidence than his aggressive side as he moved quickly to strike a deal with consultant's leaders. Mr Reid welcomed the deal by saying, "I think it was worth going the extra mile or two to get a sensible compromise which will benefit National Health Service patients."

With his appointment coinciding with that of the new BMA Chairman Jim Johnson it could be a good time to start building trust again between the NHS and the government. Mr Johnson is keen to improve relations and began his tenure with a conciliatory note: "Let's try to draw a line underneath a lot of what has happened in the past."

However, it is almost certain that confrontations and disagreements will arise sooner rather than later and it is hard to predict which of the many sides of Mr Reid will emerge.

So far in his career he has proved himself impressively adaptable and yet he has no previous experience running a large spending department - the NHS now spends £5 million an hour. The reign of Charles Clarke at education - another gruff bruiser who moved from Labour party chairman to take on a big spending department for the first time - has not been an unqualified success. Mr Reid's team of ministers is as new to the job as he is. Four of the five - Rosie Winterton, Melanie Johnson, Stephen Ladyman and Lord Warner - joined the Department of Health at the same time.

Mr Reid has had the summer to sit back and get to grips with his new portfolio. The electoral cycle and the sheer size of his department mean he will have to find his feet quickly when parliament returns.