The British man was arrested in Bethnal Green, east London on Friday following a joint operation between City of London Police and the United States Federal Bureau of Investigations (FBI).

Detectives are not naming the bank at the centre of the alleged plot.

Officers are searching properties in the Bolton area of Greater Manchester in connection with the case.

Negotiations monitored

It is understood the original demand was made in New York.

There was then an agreement to make a payment of nearly £7m in London.

FBI staff working with officers from the City of London Police's central detective unit monitored the negotiations over the first instalment of the ransom money.

The man was arrested on Friday afternoon and is being held at a City police station.