Paris Mayor Bertrand Delanoë spent the weekend in London to campaign for his ally and fellow left-winger Ken Livingstone ahead of this week's knife-edge mayoral elections.
Mr Livingstone is beginning to nose ahead of Tory rival Boris Johnson after several weeks of neck-and-neck polling.
Mr Delanoë, seen as a rising star of the French left and fresh from re-election last month, met with members of London's French community alongside Mr Livingstone.
Some 300,000 French people live in London, where the total population is over 7 million.
All European Union citizens are eligible to vote in Thursday's election.
Mr Delanoë said: “I am here because Ken asked me and I like him a lot.
“He is a good mayor of London and a man with whom I have a personal friendship.”
Both mayors have pursued green transport policies, promoting cycling and public transport and discouraging the use of cars.
Mr Livingstone said he intends to emulate some of Mr Delanoë's policies, including setting up a cheap bike-sharking network based on Paris' successful Velib programme.
He also wants to turn part of the banks of the River Thames into a beach area by 2010, two years ahead of the London Olympics, copying Mr Delanoë's highly successful Paris Plage that gives Parisians a month long beach experience on the River Seine during summers.
Photo: Betrand Delanoë by Marie-lan Nguyen, Ken Livingstone © World Economic Forum