The defection of Tory MP Quentin Davies to Labour is a stunning publicity coup for Gordon Brown which caught Westminster by surprise.

After Mr Brown’s attempts to woo politicians from beyond Labour’s ranks, notably Paddy Ashdown, into his first Government, few thought any backbenchers might cross the floor to join him.

The chief reason for such incredulity, however, lies with Quentin Davies himself.

A wealthy merchant banker and Lloyd’s name, member of Brook’s club and keen horse-rider, he was once the butt of Labour MPs’ jokes after being fined for cruelty to sheep on his Lincolnshire estate.

After getting his first big break on the front bench under Iain Duncan Smith, who made him Shadow Northern Ireland Secretary, Mr Davies who broke three decades of bipartisan co-operation on the province by condemning Government concessions to Sinn Fein.

Mr Davies, whose wife Chantal is French, has always been on the left of the Conservative party and among its rapidly dwindling band of pro-Europeans, whose influence was crushed by the entrenchment of Euro-scepticism under successive leaders.

Nevertheless, few would have predicted he would end up a Labour MP.

He originally embarked on a career as a diplomat, joining the Foreign and Commonwealth Office after taking a first in history at Cambridge and studying at Harvard.

After seven years, including a junior posting in Moscow, he switched to the City, joining the merchant bank Grenfell & Co and later becoming president of Morgan Grenfell in France.

Mr Davies entered the Commons in 1987 for the safe seat of Stamford and Spalding in Lincolnshire. He held the constituency, since renamed Grantham, with a majority of 7,445 over Labour in the 2005 general election.

He remained on the backbenches for 11 years, having been overlooked by both Margaret Thatcher and John Major, and it was only when the party was in opposition that he was given his first front bench job, as pensions spokesman, and later a junior Treasury and defence spokesman, under William Hague.

He was one of the Tory politicians whose careers were briefly rescued by Iain Duncan Smith, who promoted Mr Davies to the Shadow Cabinet to shadow Northern Ireland.

During his two years in the post, his tone was often bitterly critical of the compromises made by Tony Blair to republicans as part of the peace process and it was Mr Davies who ended cross-party co-operation on Northern Ireland by attacking the granting of Commons offices to Sinn Fein MPs despite their refusal to swear the oath of allegiance to the Queen.

The arrival of Michael Howard ended his brief term in the Shadow Cabinet and he returned to the margins of the Tory party at Westminster. He was among a group of pro-Europeans who sided with David Davis in the party’s leadership election of 2005, after Kenneth Clarke dropped out, in the hope he would resist taking the Tories further in the direction of Euro-scepticism.

David Cameron’s victory ended such hopes, even though the Tory leader later shelved a pledge made during his election campaign to withdraw Conservative MEPs from the Christian Democrat grouping to which they are loosely attached in the European Parliament, the European People’s Party.

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