Salmond is back by popular demand, but can he restore calm to a troubled party?

It has been criticised as one of the biggest political U-turns of recent times, but Alex Salmond's decision to return to the leadership of the Scottish National Party is likely to leave his opponents feeling most uncomfortable.

In the past 10 weeks, membership of the SNP has grown. More than 1,100 people have signed up as a result of Mr Salmond's return, taking membership to 9,350 and rising.

When the 49-year-old MP for Banff and Buchan surprised everyone by his sudden change of heart, he admitted he had never expected to be applying for the job again, but said "time and circumstances change".

He claimed an avalanche of letters, phone calls and e-mails asking him to stand when John Swinney resigned, amid a campaign of bitter infighting and backstabbing within the party, changed his mind.

With Mr Salmond back in charge, the SNP, which used to punch above its weight under his previous leadership, hopes it will once again ruffle feathers north and south of the border.

That the man has charisma cannot be denied - just ask the 76 per cent of grassroots SNP members who voted for him to return as their leader. But for the party to win over the majority of Scots to the idea of independence he must help, rather than overshadow, fresh talent among party activists.

Below the charm and twinkle in his eye which endears him to so many women of a certain age in the fishing ports and farming communities of Banff and Buchan, Mr Salmond has a ruthless streak.

The media, by and large, north of the border are pro-Unionist and anti-SNP. Getting the message across needs somebody with charisma, ego and talent, someone capable of going for the jugular.

He rose to prominence in 1988 when, as the cocky leader of just four MPs in Westminster, he interrupted the Budget speech of the then Chancellor, Nigel Lawson, with the sound bite: "Tax cuts for the rich, poll tax for the poor, nothing for the NHS."

It was a move which raised his profile and got him ejected from the chamber for a week.

However, Mr Salmond has never been afraid to speak his mind. He aroused controversy when he opposed Nato action in Kosovo during the 1999 Scottish election campaign, and hit the headlines with calls to impeach Tony Blair for the war on Iraq.

He has spoken out against the Scottish Parliament's extravagant spending on the Holyrood building, maintaining that a parliament in a hut can be just as effective as one in a palace.

He is self-assured and can produce sound bites with the best, but, unlike the nationalism stereotypically portrayed by the pro-Unionist media, he doesn't go in for English-bashing or jingoistic tartan fanfares.

He is an intellectual but, as the grandson of a plumber and son of a civil servant, the boy from Linlithgow who gave up a promising career as a senior economist at the Bank of Scotland has the "common touch".

During the recent leadership election debate he spurned a chance to debate his ideas with rival challengers and instead attended the opening of a new curry restaurant in his constituency because he had "given his word" to the owner he would.

The second of four children, he joined the SNP as a student. As a committed left-winger he became a leading member of a socialist republican faction inside the party, and rose to party leader at the age of 35.

During that time he successfully led the party into the new political dawn of devolution for Scotland and repositioned it as a more social democratic and pro-European party.

However, after 10 years in the job he suddenly resigned to "spend more time with his family", which turns out to have been true rather than a euphemism for some other darker reason.

Four years later, a re-energised Mr Salmond claims to be ready to once again take on the task of modernising the SNP.

A keen gambler, Mr Salmond is staking a lot on his own ability to charm an electorate which has in the past few years become increasingly disillusioned with the idea of devolution and with Scottish politics as a whole.