Chris Bain had a unique opportunity this week - the chance to meet US President George W Bush.
Mr Blair and Mr Bush at the meeting this week
As protests over the president's visit took place in Trafalgar Square, the director of aid agency Cafod was in Downing Street talking to Mr Bush and Tony Blair about the battle against Aids.
Here he reveals his impressions of an "engaging and attentive" US president.
It's not every day that you shake the hand of the world's most powerful man and have an opportunity to feed into an initiative that could help save millions of lives.
As director of the development agency Cafod, I was invited to 10 Downing Street to join a round table discussion with President Bush and Tony Blair about an issue close to Cafod's heart - the HIV and Aids pandemic.
Cafod has a widely acknowledged experience in dealing with HIV and Aids issues across the developing world and it was extremely rewarding to be invited to share our experiences with a man who could really make a difference to the growing problem.
The meeting was pulled together incredibly quickly by the Department for International Development and brought together representatives from the five African countries of Ethiopia, Zambia, Nigeria, Uganda and Kenya and key actors in HIV and Aids work.
It was the only such meeting scheduled during President Bush's visit to London and as such really encouraging to those of us who work to tackle the realities of HIV and Aids at the grassroots every day.
Following preliminary meetings and lunch, it was time to wait for the main show and everyone borrowed a place around the Cabinet table.
Mr Bain: The world leaders showed commitment to beating Aids
Secretary of State for International Development Hilary Benn helped pass the time by telling us in whose seat we were sitting.
One delegate was less than impressed by the classic décor of the famous room, remarking that the paintings chosen to decorate the Cabinet Room walls were a little bit dull.
They certainly would not have been my first choice - rather staid representations of the first prime minister to live in 10 Downing Street, Sir Robert Walpole, and the local St James Park.
But Mr Benn, in good humour, remarked that Walpole himself would not have found them dull.
Then suddenly the president and prime minister swept in, accompanied by US National Security Advisor Condoleezza Rice and Secretary of State Colin Powell.
The two world leaders took time to work their way round the room shaking everyone's hand - a nice gesture that was repeated an hour later when they moved on to Bush's next appointment.
Once the comment was clarified, Bush joked: "Sorry, I don't speak English well, I'm from Texas."
Bush certainly is not a wet fish merchant when it comes to greetings - his handshake is bone squeezingly firm and he looks you straight in the eye.
I was surprised at the informality of meeting; with Benn working hard to make us all feel at ease. Although slighter shorter than I had imagined, Bush was engaging and attentive with a winning self-deprecating charm.
At one point Bush misunderstood one of the African delegates, who said that the HIV issue was an uncomfortable situation.
The president at first thought the comment was a suggestion that he himself was uncomfortable with the situation.
Once the comment was clarified, Bush joked, "Sorry, I don't speak English well, I'm from Texas."
As soon as the prime minister opened the meeting, a swarm of about 30 photographers swept in, snapped away madly for a few minutes and then disappeared again.
Neither Blair nor Bush seemed to notice the media scrum.
I came out of the meeting mostly hopeful and thought Blair and Bush were genuinely committed to eradicate HIV and Aids.
A measure of this will be both countries turning their words into action.
Early next year a UK/US taskforce will be launched to work in partnership with the government, business, and civil society in the five countries represented at the meeting.
Bush was clear that this taskforce is not just there to hand out drugs, important thought they are.
It would promote prevention and treatment strategies but also address the factors that accelerate the spread of HIV and Aids, including lack of education, gender inequality and poverty.
It was this last point that was probably fudged during the meeting.
To reduce poverty will require finance for huge development programmes and the political will and leadership for this is yet to emerge.
That said, there was a strong feeling that both the UK and US are ready to listen to their African counterparts and support African leadership in fighting the virus that is devastating their continent.
As Bush said, it is time to be honest about HIV and Aids.
For all the glitz and glamour of the day, it was impossible to forget the reality of why we were all there.
One woman Asunta Wagura, from Kenyan Women with Aids, quietly asked at one point that in the newly invigorated fight against HIV and Aids, we should not forget to involve those living with the virus.
While the most powerful man in the world can make people sit up and listen, we must all ensure that the anonymous, powerless millions are given a voice to inform our decisions.