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The loss of foreign tourists is 'the biggest single thing' to hit London's economy since the start of the pandemic, according to a senior City Hall official.
Mayoral chief of staff David Bellamy said spending by overseas visitors was more significant than office workers.
Central London businesses which rely on overseas visitors are said to have missed out on £7.4bn.
By contrast, the loss of income from commuters now working from home is an estimated £1.4bn.
Mayor Sadiq Khan wants the government to help fund a global advertising campaign to attract foreign tourists back to the capital.
Mr Bellamy said it would follow the 'Let's do London' campaign aimed at domestic tourists last year.
"The next phase of response is very much about international tourism and that's probably, in our analysis, the biggest single thing that the London economy is missing given the Covid impact and so we're in discussions with the government at the moment about the potential of funding for international tourism promotion overseas," said Mr Bellamy.