If you try to suggest that saving works of art from being sold abroad has less to do with the essentials of life than charitable work such as famine relief or cancer research, the normally laid-back and mild-mannered David Barrie becomes very animated.
"Well, no, I would challenge that," he interrupts, leaning forward in his chair. "It all depends what you think life is about, and life is not just keeping body and soul together. There is far more to a decent life than just staying alive. Obviously it's important that you do stay alive, and the humanitarian charities quite literally have a vital role to play in that sense.
"But our job is to help make life worth living by giving everyone the opportunity to encounter great works of art in public collections. Art can quite literally change people's lives: it can change the way people see the world, it can open up realms of imaginative possibilities, it can give them solace when they're feeling low, inspire them to achieve great things. It would be impossible to enumerate the ways in which contact with art can enrich people's lives."
Barrie goes even further, arguing that a cross-cultural approach to collecting and exhibiting art can be a force for peace in the world: "It may sound a bit grandiose, but one of the services museums and galleries can perform is giving everyone the chance to see and admire the achievements of other cultures and recognise, across the divisions and barriers of history and culture, our common humanity. It's hard to go to war with people whom you recognise as being just like you, with the same fears, needs and concerns."
Barrie has been running the National Art Collections Fund, commonly called the Art Fund, for 11 years. He is an expert on John Ruskin, and operates from an elegant office in an 1861 Victorian house opposite the Natural History Museum, which was first occupied by the pre-Raphaelite painter Sir John Millais. The fund's committee meets once a month in Millais' old studio to look at the works for which contributions are being sought.
It was Barrie's idea to mount Saved!, the current exhibition at the Hayward Gallery in London, which marks 100 years of the fund and which he says is "a rare opportunity to blow our own trumpet". It showcases 400 of the 500,000 works which the fund has helped to buy since this unique charity was set up by a group of enthusiasts trying to stem an artistic haemorrhage to the US and Germany in 1903.
The exhibition contains familiar favourites such as the Rokeby Venus by Velazquez, which is probably worth £60m or £70m now and was bought by the fund in 1906 for £45,000. That's about £2.5m in today's terms, but the sum was considered outrageous at the time, not least because it was nine times the amount the National Gallery had for purchases that year.
It also has causes celebres such as The Three Graces by Canova, saved for the nation with much fuss in 1996, and brilliant masterpieces like Epstein's Jacob and the Angel and Botticelli's Virgin Adoring the Sleeping Christ Child, the £10m purchase of which four years ago attracted the fund's all-time record contribution of £550,000.
While the Daily Telegraph's critic praised the exhibition and said that almost every work 'grabs you by the lapels', the man from The Guardian concluded that it was "the naffest exhibition I've seen in years". Barrie, back in mild mode now, shrugs at the criticism and smiles. "Plenty of people are going along to see it," he says. "And that's the main thing."
He's hoping the exhibition will boost the fund's membership, which has recently slipped back 8 per cent to 80,000, and looks forward to the extra income, clout and sense of purpose - not to mention legacies - which higher membership brings. Two exceptional legacies gave the fund £6.5m in the past three years, helping to offset the fall in the value of its investments and leaving total funds at £28m last year compared with nearly £33m in 2001. Grants worth £4.25m were made in 2002.
Meanwhile, Barrie's mind is turning to future tasks, such as developing the activities of the fund's 500 volunteers and its campaigning role, which he says is becoming every bit as important as the business of helping to buy important works that would otherwise leave the country or disappear into private collections. One current campaign is to persuade the Treasury to give people income tax relief if they give works of art to public collections.
But his main concern is the long-term future of the funding of museums and galleries which, ironically, is called into question partly as a result of the fund's greatest achievement of recent years - the four-year campaign to ensure free access for everyone to the country's most important museums.
But free admission has left institutions more dependent on public money to maintain themselves and fund acquisitions, and Barrie says ministers have failed to face up to this. Instead, they are trying to hand these tasks to the Art Fund, the Heritage Lottery Fund and the cash-starved National Heritage Memorial Fund.
"If you accept the principle that the Government is responsible for galleries, anyone like us who steps in from time to time is letting them off the hook to some extent," says Barrie. "The question is how far should it go, and the answer is not too far. There has to be a constant tension.
But in the past decade the trend has been for funding to go steadily downwards and the balance has definitely gone the wrong way. We should be operating at the margins and should not be expected to do the whole job."