Today's arrests follow an investigation into an apparent online scam whereby £1 million was siphoned off the accounts of customers of two banks.
The alleged scam involved emails, that appeared to be from the banks, containing "malware" which corrupted the recipients' computers.
T/DCI Jason Tunn of the Metropolitan Police's Cyber Crime Unit said he suspects they are dealing with an "international and organised crime targeting a number of bank customers in London and across the UK".
"The victims have been hoodwinked by malware-carrying emails purporting to be from their banks, and subsequently had money taken from their accounts," he said.
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Guillier conceded a "severe defeat" defeat to his supporters as the result came in.