Ex British Chamber of Commerce chief John Longworth told the French bureacrat that "no trade deal is better than a bad trade deal" and said the 17.4million Brexit voters would "not be prepared to negotiate away our newly-won economic freedoms" to secure a trade deal with the EU. He stated that more than 80% of Britain's economy was services-based and he saw the country's opportunities for future growth in the same sector. "To enter into an agreement on goods with no agreement on services would be a very one-sided arrangement and I don't think that could be attractive for us".
The Labour mayor was a strong supporter of the remain campaign and has since vigorously argued for the United Kingdom to stay in the EU's single market and customs union, or for London to be granted its own deal, especially on maintaining rules on banking and financial services.
He said he was convinced that the leave campaign would win a second vote by a larger margin than the 52%-48% in 2016, but to a hold a second referendum would "set a precedent for revisiting any democratic decision made in future".
But this is not a precise forecast, and there remain many factors that could change these scenarios for better or worse - not least the precise details of any deal negotiated with the European Union, or other countries.
A small number of countries initially preferred the third option but changed their minds when ministers said they couldn't start negotiations until March 2019.
Britain's forthcoming exit from the European Union was the main reason for a 37 per cent decline in new jobs available in London's financial sector last month, according to a report from recruiting firm Morgan McKinley released on Thursday.
The most optimistic Brexit scenario outlined, of a two-year transition period leading to single market membership without the customs union, would still lead to a loss of 176,000 jobs and £20.2 billion in investment.
London Mayor Sadiq Khan said Britain would be shunted into a "lost decade" of low investment with hundreds of thousands of lost jobs if it fails to agree a trade deal with the EU.
"We will not be paying for market access", he told reporters ahead of the gathering.