She is, she says with a guffaw, “the maniac who signs the big cheques”. That, Dame Vivien Duffield says cheerfully, is how the rest of the board of the Jewish Community Centre for London regard her.

But of course this philanthropist dynamo is very far from being a maniac, although she certainly signs the big cheques. The latest, for £25 million, is, she says, the largest single donation she has ever made. Via her Clore Duffield Foundation, it goes to the JCC, which received unanimous planning permission last week from Camden Council to raze the old Mercedes showroom on London’s Finchley Road and build a new, state-of-the-art centre to cater for Jews across the religious and political spectrum. The plan is to open in 2013.

The dame’s donation is only half of the costs of the new centre. Bricks will not be laid, she says, “until a good slug of the other half of the money” is raised, making the JCC the biggest capital project, at £50 million, ever undertaken by the Jewish community in Britain.

The JCC project was originally much more ambitious, including a pool and a sports centre. But then, said Dame Vivien, “reality hit” and the full implications of what such a building was going to cost — all 80,000 sq ft of it — made the board take a step back. The pool costs alone were, according to the JCC chief executive Nick Viner, “just prohibitive”.

Architects Lifschutz Davidson Sandilands have now produced a more modest, but stunning, community centre. Fourteen residential flats mark one side of a three-storey building while an enclosed piazza, linked with amenities on the ground floor, will offer an “external room” giving out on to Finchley Road, allowing imaginative use of the space for a marquee or even a community barbecue.

There will be a Jewish nursery school offering full day care for children from six months to five years old; and, though the main scheme only includes four disabled car parking spaces, the nursery will have, says Dame Vivien firmly, “a proper drop-off area and parking so that parents can escort their children into the building”.

This project has been Dame Vivien’s baby ever since she came back, bursting with enthusiasm, from visiting the Manhattan JCC in New York.

At the launch breakfast she held in October 2003 to initiate the scheme she said, optimistically, that she hoped the building would be up and running in five years, a statement she made “thinking that we could find something suitable to buy. But there wasn’t anything.”

With the economic downturn “the costs got immorally high. Little by little we looked at what we really wanted.”

Dame Vivien’s enthusiasm and energy reduces somewhat when asked about the London Jewish Cultural Centre, which has itself received planning permission from Barnet Council to build a youth wing at its Ivy House site in Golders Green. It seems, to say the least, odd for two Jewish cultural organisations to be asking for money from the community at the same time. Dame Vivien will say only: “We feel that what they do is a complement to what we do. We are not the same as the LJCC and we feel that we are going to attract, and that we must attract, a different public. They have a fantastically good programme, and hopefully, what we offer will be… different.”

Clearly this is not the most comfortable line of questioning. A call to the LJCC elicits a polite comment from its chief executive, Trudy Gold: “The LJCC is delighted that the JCC’s plans for Finchley Road have been approved. We welcome the development of more facilities designed to engage London Jewry in communal activities. We wish the JCC every success.”

So everyone is being very well-behaved, but the JCC project is going to require many millions more funding than the LJCC. Dame Vivien is only too aware of the problems.

“To be perfectly honest, we weren’t sure we were going to get planning permission. Now that we have it, the fundraising can start. I think it’s going to be very hard. People are cutting back. There is no doubt that this is not a tug-at-your-heart cause, but then none of the great cultural institutions was: you’re not going to die because you don’t have a library or museum, but your life is enriched by it.”

Her target audience, she says, are those people who have not previously been engaged with the Jewish community. “I do not think that the big givers to Norwood or Jewish Care are going to abandon those causes, in fact I know they’re not. But I really believe that there are people who are not actively engaged at the moment who could be attracted by this scheme.”

Certainly the dame is confident. She is unfazed by the prospect of antipathy to a Jewish building in the face of rising antisemitism and attacks on Israel.

The JCC, she says, “is nothing to do with my Israel projects. I do what I do in Israel, where I have built three community centres. This is about putting people here in the UK back in touch with their Jewish side. It is a fantastic project, and it is my last idea.”

Is it her last hoorah, then? “No,” she says, crisply. “It’s my big hoorah.”