Surviving coffee with Colin

Given that we are not talking a mug but pints of the stuff, let’s go with the coffee.

Ms Lewis, the woman responsible for overseeing Oxfam’s campaigns with celebrities, warms to her subject as she describes what must have been the photo shoot from hell for the Oscar-winning actor.

“Well, we heated the first vat,” she explains. “But the problem with coffee when you’re dumping that much over someone’s head, it just gets colder and colder. By the end it couldn’t have been very nice.”

A nice idea though to boost an Oxfam campaign for free trade — and needless to say The King’s Speech star still managed to look cool in every sense.

And at least the smell was bearable. Not like the time she covered REM’s Michael Stipe in milk.

“His hotel room ended up smelling of baby poo,” she laughs. “Oh my God, there was milk everywhere. It was a plush hotel. I don’t think they knew what we were planning. We just went in and covered the floor with plastic sheets.”

But there were no complaints from the star. With Claire there never are. Even when dumping chocolate over the head of Oxford’s Thom Yorke had the unforeseen effect of making his eyes sting, the supposedly moody Radiohead man was sweetness itself.

For the stars trust Ms Lewis, who started working with Oxfam as a bookshop volunteer before going on to become the charity’s international artist liaison manager.

Whether it is a case of exposing themselves to uncomfortable photo shoot indignities for the latest campaign she has dreamt up, or being escorted around vast refugee camps in Africa, they know their fame will never be put to better use.

There is, of course, nothing new in charities enlisting famous people to champion their causes. Back in the 1950s Marilyn Monroe visited US orphanages, the Beatles famously donated to Oxfam in the 1960s and actress Julie Christie campaigned on Cambodia in the 1970s. But in this celebrity-obsessed age, Ms Lewis, 43, ensures Oxfam benefits to the maximum from its famous friends.

“People do not want to see famous white people holding starving babies,” said Ms Lewis. “Oxfam has moved away from that kind of thing and I don’t believe it washes with the general public anyway. We want to see the situation where people tell their own stories but these stories are amplified by the celebrities.”

The sufferings of a woman sitting in a refugee camp in Uganda has next to no chance of ever getting her story heard — but if it is told to a Hollywood star, who then recounts it to camera, the story will be heard by millions. It really is that simple.

She well recalls one celebrity telling her, ‘I don’t want to be an ornamental mouthpiece”. But, for her, it boils down to them being mouthpieces for those in desperate need.

And no longer is it a question of just encouraging donations. Oxfam’s approach these days is to use global ambassadors such as Archbishop Desmond Tutu, Coldplay, actor Bill Nighy and Scarlett Johansson, who have built up knowledge of the charity’s work, based on foreign trips over years.

“What we want is someone who knows the organisation and who can speak in a creative way, with integrity about Oxfam. If you are putting them up to speak on our behalf, they need to know what they are talking about.”

Ms Lewis said she considered Oxfam ambassadors as part of a team, all able to open doors that don’t open to Oxfam staff. Helen Mirren’s lobbying behind the scenes, for example, helped secure meetings with politicians on arms control and closing loopholes in the arms industries.

She used to tease Colin Firth that he could now do the ‘Oxfamology’ exam, as he read almost all Oxfam’s policy documents to understand the issues. They are currently working together on a secret project to mark the Oxford-based charity’s 70th anniversary.

Ms Lewis’s own time with Oxfam goes back 25 years, when, after working as a volunteer in London, she agreed to stand in for a shop manager, who was ill. She arrived in Oxford 12 years ago and now lives in Fyfield, with husband Marcus, whose work as an engineer regularly takes him to Africa, and their daughters Lula, 13, and Freya, 10.

She has introduced numerous celebrities to Africa, who respond to poverty in different ways. One visit that remains most vivid in her memory involved one of her least well known travel companions, Dr Mick North, whose five year-old daughter Sophie, was killed along with classmates by a gunman at their Dunblane primary school.

“I remember him meeting a woman whose daughter had been shot. The two of them went off and just sat on a hill talking.”

The impact that celebrities can make as speakers never fails to impress her. She recalls last December seeing the Bollywood star Rahul Bose reduce an audience to tears, before overseeing an auction that raised $1m. These are people who can hold an audience and are so eloquent. No one from Oxfam could have done that.”

Others, such as Annie Lennox, push forward their own policy initiatives. Ms Lewis has fond memories of sitting in the singer’s garden, throwing around ideas which led to the development of The Circle — an initiative bringing together influential women using their skills and connections to help women living in poverty.

Sometimes she is faced with going to Oxfam ambassadors with seemingly frivolous requests.

“They are happy to help us in fun ways as well as the more serious elements of Oxfam’s work and these projects are great to work on. An example of how our ambassadors support us is Helen Mirren’s involvement in the Big Bra Hunt. My colleague Raakhi Shah has been working on a great campaign to try and get a million bras donated by Oxfam.”

Dame Helen, photographed clutching a bra, declared: “Before I heard about this campaign I had never thought to donate my bras to Oxfam. I’m sure many women have a number of bras stowed away left untouched for years. The Big Bra Hunt really highlights how every last item donated to Oxfam can be used in a truly unique way.”

A couple of sentences, but it would be difficult to put a price on the level of media coverage secured.

For the stars, such involvement inevitably brings accusations of self-promotion and the risk of derision for their do-gooding attempts.

“The people I work with hardly need to build their profiles. They are already at the top of the tree,” said Ms Lewis. “It’s like one of them once told me,’ which is better — to tell the grandchildren you used celebrity to make a difference, or get a table in a restaurant?’.”