The Liberal Democrats’ biggest donor has become one of Britain’s most wanted men after being convicted of stealing millions from a former Manchester United boss.

Michael Brown, 42, who was tried in his absence after skipping bail, posed as an international bond dealer, pretended his father was a Lord, claimed connections with royalty, and promised investors staggering returns of up to 50%.

His numerous lies, including claims he had clients “vetted” by US embassy officials and Special Branch before accepting their money, helped him pocket nearly £8m from ex-Manchester United chairman Martin Edwards.

The former football chief, one of an international array of victims who lost fortunes, little realised he was entrusting his money to someone who had not even passed his maths O-level.

Altogether he and the others gave the Glasgow-born businessman 57.7 million US dollars (£36m), of which a record £2.4m was donated to the Lib Dems’ 2005 General Election war chest.

While the Electoral Commission decided it was “reasonable” for the party to regard his seeming generosity as “permissible”, Brown’s conviction for theft and other offences will almost certainly heap further embarrassment on them.

There may even be renewed calls to give it all back.

An American lawyer has already launched a High Court bid for the return of hundreds of thousands of pounds he claims the crook handed to the Lib Dems.

London’s Southwark Crown Court heard the picture of political largesse presented to party grandees was simply part of a carefully crafted “illusion of wealth and influence” designed to give him the social acceptability he craved.

The crooked businessman - who will not be sentenced until he is caught - channelled his gift to the Lib Dems through a company called 5th Avenue Partners.