A local authority like no other, it promotes London as a leading world financial centre on an international scale, as well as managing its street cleaning and its roads.
As he approaches ten years at the helm of the Corporation's PR department, Tony Halmos is humble about his position - despite just having overseen a radical change in its electoral system.
The son of a Hungarian couple who fled to England before the Second World War, Halmos started his love affair with the political world via his parents' interests in current affairs. But, unlike his parents, Halmos became a political activist at a young age.
'I have always been a political animal, I was following the general elections when I was 12. I coloured in maps of the results of the general elections when I was this age instead of football charts like the other children,' he says.
Halmos worked as an assistant organiser for the TUC and as a national organiser for the SDP before joining Hill & Knowlton as associate director of public affairs. He joined the Corporation in 1994.
London's Square Mile sees an influx of 300,000 commuters every day that staff trading floors and banks. But the area offers more than a financial district; it is a major arts and tourist centre and home to 8,000 residents.
The Corporation has been forced to reform in the face of opposition from the Government, which threatened to abolish it and merge sections of the Square Mile with the surrounding local authorities. This is where Halmos dipped into his experience in public affairs and, in conjunction with the chairman of the policy and resources committee, engaged in a fierce campaign to guarantee the future of the authority.
The Government relented, and permitted the Corporation to remain on the condition that its voting system was reformed to include the wider business community and that the Corporation continued its work 'outside the City walls'. Its responsibilities extend to the wider communities including the maintenance and management of many of London's parks and its social housing stock.
So Halmos was charged with publicising electoral reform and to entice the staff on the busy trading floors and banks to cast a vote in the local elections. Despite scepticism from the press, the campaign rustled up 7,000 extra votes from the business community when voters went to the polls last week, and Halmos says he is satisfied with that. 'We had over a 30 per cent turnout and we are happy with that because that's reasonable for local government elections these days.'
The Corporation has a mammoth £300m budget, yet only 8,000 residents.
Halmos admits: The (previous voting system) was completely bonkers and antiquated. We had to reform it. Something that was created in 1801 is hardly going to work without a change.'
Friends and ex-colleagues describe Halmos as a political anorak. They include Media Strategy managing director Charles Lewington, who says: 'What the Corporation and Tony understands is that the Corporation will be here when many politicians are gone and long forgotten. As a result, the Corporation has always attached the highest priority to being impartial when working with whichever authorities are in power and this is a tribute to Tony.'
While his working day takes place in the City, Halmos retreats to a newly purchased second home in the Cote d'Azur to relax and his spare time is taken up with setting up a charity in memory of his mother, a former social worker from Budapest. The yet unnamed charity will be based on the work Halmos does to form links between doctors at Great Ormond Street Hospital and a children's hospital in Budapest.
Halmos's success in PA is due partly to the sincerity in his tone when talking about whatever subject he chooses - be it his work, his love of France or his disappointment with the political world when the SDP crashed.
But when he relaxes with a glass of wine in his cottage on the Cote d'Azur, I don't expect it keeps him up at night.
1973: Research associate, Templeton College, Oxford University
1978: Assistant organiser of organisation and industrial relations
department, Trades Union Congress
1982: National organiser and local government officer, Social Democratic
Party and the Liberal Democrats
1989: Associate director, public affairs, Hill & Knowlton
1994: Director of public relations, Corporation of London