Alexander faces tough task as he is named new Chief Secretary

He has already had an election, a birthday, a new baby and a promotion to the Cabinet this month, but things are showing no signs of slowing down.

Danny Alexander had taken some delayed paternity leave last week, after the birth of his second daughter eight days ago. But, last night, his domestic duties were rudely interrupted by the news that he was being thrust into the engine room of the Government's campaign to slash the national debt.

The Liberal Democrat MP for Inverness, Nairn, Badenoch and Strathspey was a virtual unknown outside his own party before the election, but in a few short weeks he has emerged as one of the driving forces behind the creation of the coalition government – and now a central figure in its most important task.

As Nick Clegg's chief of staff, he was a key member of the Lib Dem team negotiating the terms of the coalition deal; when he was originally rewarded with the post of Secretary of State for Scotland, it was universally deemed an appropriate position for someone of his limited experience and seniority. And he was Scottish, to boot.

Red-haired Mr Alexander arrived in Parliament in 2001, after winning his first-ever election. But he already had a long record of political service, having joined the Lib Dems in 1993, and subsequently worked as a party press officer in Scotland and as an aide to the Scottish Lib Dem leader Jim Wallace during the 1997 election. He has also worked as a PR man for the European Movement and Britain in Europe, and then, in a move back home, for the Cairngorms National Park.

Once in Parliament, he did not make an immediate impact – in fact, he first came to public notice when it emerged that his election campaign had benefited from a £2,500 donation from a friend, the industrialist Chris Haskins. Lord Haskins, it was subsequently pointed out, was a Labour peer, and was later expelled from the party for funding an opponent's campaign.

Mr Alexander quickly made it on to the Lib Dem front bench, and within two years he was part of the core Lib Dem team, ultimately becoming the work and pensions spokesman, at the right hand of the new leader.

Notoriously, he was with Mr Clegg on a plane to London when the leader criticised Steve Webb and Chris Huhne, other members of the Lib Dem team – and suggested that David Laws was not enjoying his education brief. "The Tories have left him no space," Mr Clegg apparently told Mr Alexander. "But he's got a forensic intelligence; he's probably the best brain we have."

Mr Alexander will now attempt to replace his party's best brain as Chief Secretary to the Treasury, but without the fiscal reputation of his predecessor. And, as a concerned Tory pointed out last night: his economic expertise amounts to a third of the degree in philosophy, politics and economics he took from Oxford in 1993.

Mr Alexander's wife, Rebecca, gave birth to their daughter Isla last Saturday. They already have one daughter, Isabel. He turned 38 soon after he was promoted to the Cabinet earlier this month. But he's unlikely to be celebrating much any time soon.