It could be said that Tim Knox is Sir John Soane reincarnate. Some 200 years separate them, but they both share a love of collections and their display, and a passion for architecture that has infiltrated their personal as well as professional lives. And like Soane, Knox has renovated his own 18th-century property to house his diverse private collection.

Parallels certainly. But the man who has got the directorship of Sir John Soane's Museum, London, cannot quite remember when he first came across Soane and his passion for collecting. 'I'd like to say that I was brought here in a pram,' he muses. 'I suspect I really found it when I came here as a young student at the Courtauld.'

Knox is three days into the job when I call on him at Number 13 Lincoln's Inn Fields. We talk in his office on the third floor, which, he tells me, was Mrs Soane's old bedroom. He is surrounded by Soane's own furniture, including Mrs Soane's daybed, which has been turned to face the wall, much like a naughty child. Drawings and paintings of Soane and his family are all around.

Knox takes over the reins of this national museum from Margaret Richardson, who retired in April after ten years. He says he intends to do a lot of 'listening, looking and learning' before deciding on any changes he might make.

One immediate modification, though, was a request to the museum trustees to change the job title from curator to director. Knox inherits a static collection that under the law according to Soane cannot be re-displayed. So, essentially, it is a non-curatorial role. Richardson had told Knox she always used director when liaising with international colleagues. 'It really is establishing a status,' he says.

Knox, an architectural historian, studied Anthony van Dyck and English 17th-century painting at the Courtauld Institute of Art in the early 1980s. He worked as an archival researcher of national museum artefacts before moving to the Royal Institute of British Architects' drawings collection as an assistant curator.

Then he spent nine years at the National Trust, first as an assistant architectural adviser, then as an architectural historian, before becoming the head curator. He was responsible for buying some of the trust's properties, notably the Victorian Tyntesfield estate near Bristol, and acquired and displayed works of art for the interiors.

He managed a staff of 50 across the UK (excluding Scotland), and when the trust went through an organisational review in 2002, he coped with a 'pretty hairy time' when all employees had to apply for their own jobs.

The decision to move from the trust came partly because of the 'interesting' politics, partly because the trust has plans to leave his beloved London, but also the headier levels of management would have led him further from hands-on work with collections and the historic houses.

Knox almost didn't apply for the Soane job but a friend persuaded him. 'I always assumed it to be the preserve of very senior architectural historians. Almost a place where people would come to retire and write books and contemplate their former triumphs.'

That certainly was not true of his predecessor. Richardson introduced temporary exhibitions to the museum, catalogued the collections and set up an education unit. She also instigated the five-year restoration project for Number 14, the house that Soane built and rented out.

The idea is to create a children's education unit, a room for the Robert Adam archive, re-establish Soane's collection of architectural models, and have research facilities. Knox has asked his trustees to give him two months to digest and review the plans. Without a collection to develop, this will be his big project.

He says he is trying to convince himself that the plans will make the best use of all three premises (Number 12 was Soane's first home). Instead of only aiming for the £2m calculated to renovate Number 14, perhaps something like £10m, he says, may be wiser.

The museum, which costs £1.1m to run annually, is surviving virtually hand to mouth with reserves of about £100,000. 'If you can't raise funds for this museum then we all may as well go home.'

Knox is a flamboyant character, not devoid of eccentricities (he owns up to having morbid tastes in art). He is extremely personable, with a quick wit. I wonder if being surrounded by Soane's fascinating collection will be enough to fend off this need to collect. 'I can perhaps sublimate my acquisition urges into fundraising for the museum,' he says.

Knox's passion for collecting began in Fiji and Nigeria, where he grew up. He recalls pictures of himself as a two-year-old displaying his shells and natural history collection. When he went to secondary school in Britain, he started visiting country houses and it really took off.

His first serious acquisitions were 19th-century religious artefacts, statues and pictures - 'things a lot of people find quite uncomfortable'. He also collected crucifixes and Victorian embossed funeral images, and Victorian natural history. Many of the early items have been sold and his tastes have moved on to 19th-century sculpture, but he still has a penchant for religious art.

Most of his items now come from Portobello Road market in west London. He is there every weekend and appears amazed that the only museum director he sees there is Timothy Clifford of the National Galleries of Scotland.

'Whether it's the miserable museum salaries or the fact that people have families or other commitments, collecting is no longer a part of museum curators' lives. I don't have a private income or anything, but I've always thought that it was one of the things I absolutely had to do. I'm afraid it's an illness that can't be got rid of easily. I go into a bit of a decline when I can't exercise that.' But unlike Soane he does not collect contemporary art.

His collections are housed in the 20-room house he calls Malplaquet in Stepney (an area known for its housing pressures), east London, which he bought from the Spitalfields Historic Buildings Trust as a ruin five years ago. It is meant to look like it hasn't been freshly restored, he says. He shares it with his partner and two dogs; their neighbour is

Charles Saumarez Smith, the director of the National Gallery. Knox is quick to give Richardson the credit for putting the Soane museum on a confident national footing. He says there is a good understanding with the Department for Culture, Media and Sport that the museum 'will never be a Great Court. Experience has shown that advertising the Soane museum is the last thing we want. We cannot cope with that sort of visitor volume'.

The director's role, he says, is to safeguard and champion the special atmosphere that the architecture of the museum affords. The Soane museum challenges the homogeneity among many other museums, he says. It is this that he may decide to speak up about: 'I could be a useful voice for the smaller museum among the bigger beasts.'

He has ideas for 'an amazing international club of very special idiosyncratic house museums', and an alliance of architectural museums. At a push, he reveals concern for the way the public circulate around the museum and says he wakes up in the morning trying to fathom a way to bring Soane, the man, alive to the visitors. And a major bugbear (Knox mentions it three times) is the lack of a cloakroom for visitors.

Though Knox is relatively unknown to the wider museum community, those who know him say one great collection may well suit his talents better than a gaggle of historic houses. Knox says at the NT he always had the chance to be influential, but decisions were made at a different level. 'It is a chance to cut my teeth as a director, as someone who can change the destiny of a single institution,' he says of the Soane.

He will also add to his portfolio a major exhibition at Tate Britain on British neoclassical sculpture, working with colleagues from the Soane and the V&A. It will open next year.

He says he imagines that his generation will be one of the last to be able to work its way up without a museum qualification or a doctorate. He relied on mentors such as John Harris, the architecture historian.

Knox waxes lyrical about the wealth of knowledge among the warders at the Soane, describing them 'like beefeaters at the Tower of London. They're an institution and I really want to cherish them. Actually empower them more.' He intends to find training funds for them to 'give the best possible tour'.

In fact, it so happens that one of the warders is likely to rival Knox for the position of Soane reborn. As I leave Number 13, an attendant says that Peter, the portraiture room warder, is famously known among them as a professor on Soane and even resembles him. This is certainly not a description I can confidently make of Knox. mj