The final stage of the Scottish independence referendum campaign began yesterday on an unexpectedly invigorating note for Alistair Darling and Alex Salmond as they agreed to part in the ice bucket challenge.

The craze sweeping social media is aimed at raising awareness and funds for the neuro-degenerative disease ALS, or motor neurone disease.

The leaders were nominated by Scottish actor James McAvoy – who injected some fun into what is set to become an intense period of campaigning, dominated by issues such as currency, the future of oil and gas, and the NHS.

Darling posted a video of himself being drenched by Better Together staff outside the campaign’s headquarters in Blythswood Square, Glasgow.

Yes Scotland has revealed it has reached its target of one million declarations for Yes

Darling thanked McAvoy and tweeted a link to www.gordonsfightback.com, an awareness-raising site set up by Better Together director of research Gordon Aikman.

Aikman publicly revealed he is dying of the disease in a powerful article in the Scotland On Sunday newspaper in June.

Scotland’s First Minister, Alex Salmond, addressing members of the Scottish Parliament in Edinburgh during First Minister’s Question Time late on Thursday, the last before Scotland votes in a referendum on independence. Photo: ReutersScotland’s First Minister, Alex Salmond, addressing members of the Scottish Parliament in Edinburgh during First Minister’s Question Time late on Thursday, the last before Scotland votes in a referendum on independence. Photo: Reuters

Salmond has also accepted McAvoy’s challenge, with a time and place for his soaking to be confirmed.

The First Minister said: ‘’I’m always up for any challenge, and I’m game for this one. It will invigorate me for the next month of campaigning – but the Scottish media should be careful what they wish for, as I get to nominate who’s next for the ice bucket!’’

Meanwhile, Yes Scotland revealed it has reached its target of one million declarations for Yes.

The one-million signatures mark was a key target for the campaign at its launch two years ago and chief executive Blair Jenkins said it is encouraging that they have reached the milestone four weeks from polling day.

Former prime minister Gordon Brown joined Scottish Labour leader Johann Lamont to make the case for a No vote in Glasgow.

Brown said while Scotland spent some £40 billion a year on health, education, pensions and social security, forecasts had shown that, in the first year of independence, oil revenues would amount to £2.9 billion.

SNP deputy leader Nicola Sturgeon opened yesterday’s campaigning with a message for pensioners, insisting Brown must explain why he is “backing Tory plans to cut payments for pensioners across Scotland”.

She said: “Labour and the Tories are singing from the same hymn sheet on pension cuts and it is only a Yes vote that will protect pensioners in future from these cuts.

“Scotland is a rich country which can well afford to fund our pension payments and an independent Scotland will give pensions and pensioners the priority they deserve.”

Scottish Liberal Democrat leader Willie Rennie began the final leg of his party’s campaign to keep Scotland in the union with a visit to St Andrews in Fife.

Rennie said that people do not have to choose between being Scottish and British.

“You can stay within the UK family of nations, where we have the best things that come with being Scottish and the best things that come with being British too.

“It is the nationalists, not me, who conflate national identity with national independence and their policy of independence with the ability of the Scottish people.’’

Douglas Flint, the chairman of HSBC, warned that uncertainty over currency in an independent Scotland could lead to “capital flight’’ from the country.

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