While few people live in London's business district, those who do voted overwhelmingly in favour of staying in the European Union.
The City of London said 78.3 per cent of voters plumped for the Remain camp, meaning Leave garnered just 21.7 per cent in what's shaping up to be an increasingly tight race.
While Lambeth and Wandsworth also voted Remain, the Leave camp scored victories in Enfield, Harlow, and Broxbourne. Commentators have said strong gains in London could tip the balance back towards Remain.
It came as the City's skyscrapers were stocked with traders navigating volatile markets, as the first trickle of results appeared to show Brexit was an increasingly likely scenario. This sent sterling as low as $1.41 against the dollar.
The pound initially tanked three per cent in a matter of seconds following a surge of support for Leave in Sunderland, a key Northern city.
"The pound is plummeting as Sunderland votes heavily for Leave. Markets are very nervy at the moment ...(and) the Sunderland result has definitely altered the tone of the evening," said Joe Rundle, head of trading at ETX Capital in London.
"It's definitely tin hats time. If Leave wins there will be carnage for cable," he said, referring to the sterling/dollar exchange rate."
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