Company profits were lower than forecast, and a large amount of supposed assets held by firms were in fact disguised forms of lending to UK households.
The revision is disturbing given that foreign direct investment into Britain has collapsed, plummeting from a net £120bn in the first half of last year to a net outflow of £25bn this year.
The apparent resilience of these flows shortly after the Brexit referendum was an illusion, since the funds had already been committed earlier.
The Bank of New York Mellon, the worlds biggest custodian of assets, said there had been a marked deterioration over recent weeks in purchases of sterling stocks and bonds by real money players such as pension funds and sovereign wealth funds.
Simon Derrick, the banks currency strategist, said: The outflows from the UK began in mid-August. The big buyers are disappearing.