For almost a decade Peter Murrell and Nicola Sturgeon were the husband and wife team in charge of the SNP.
But now Mr Murrell is at the centre of an SNP finance investigation and has been arrested by Police Scotland in connection with the ongoing probe into the party’s financing.
Police Scotland said a 58-year-old man is in custody and is being questioned by detectives.
Officers are also carrying out searches at a number of addresses as part of the investigation – including the couple’s South Lanarkshire home, which has been cordoned off.
Below we look at Mr Murrell’s career to date and how he and Ms Sturgeon became key figures in Scotland’s political landscape.
Who is Peter Murrell?
Mr Murrell was born in Edinburgh in 1964 and attended Craigmount High School in the city before studying at the University of Glasgow.
He was party chief executive since 1999, and was the man responsible for the day-to-day running of the SNP, which was at one point the second largest party in the UK.
That job meant Mr Murrell was one of the most influential figures in Scottish politics, despite having never been an elected politician.
However last month he announced he was resigning with immediate effect, amid a row over the party’s membership numbers and transparency. It comes almost a quarter of a century after he succeeded Mike Russell, the current SNP president, as the party’s chief executive.
Before that Mr Murrell had worked in the constituency office of former SNP leader Alex Salmond.
Mr Murrell married Ms Sturgeon, then SNP depute leader and Scottish deputy first minister, in 2010, with Mr Salmond, the then first minister, among the guests.
The pair had first met in 1988 at an SNP youth weekend but didn't become a couple officially in 2003.
They didn't have any children and Ms Sturgeon recently spoke about her miscarriage when she was 40, shortly before the 2011 Scottish parliamentary election campaign.
Ms Sturgeon, who became both SNP leader and Scottish First Minister in 2014, quit those roles last month making way for her elected successor Humza Yousaf.
What role did Peter Murrell play in the SNP?
Mr Murrell is regarded by many as having played a key role in transforming the party’s fortunes, helping to modernise SNP operations.
While membership has fallen from the peak of about 125,000 achieved in 2018, to the recently revealed total of 72,186, the party remains easily the largest in Scotland.
And with Mr Murrell and Ms Sturgeon at the helm, the SNP has cemented its electoral dominance, having been in power at Holyrood since 2007 and won every election north of the border since then.
However, critics of the SNP under Ms Sturgeon’s leadership, both inside and outside the party, long questioned whether it is appropriate to have the key roles of leader and chief executive held by one couple.
What has Peter Murrell been accused of?
Police Scotland has been probing £660,000 raised by the SNP for Scottish independence campaigning after allegations of donations fraud – an inquiry codenamed Operation Branchform.
The probe was launched in 2021 after it was alleged money had been diverted from a “ring-fenced” fund to fight a second Scottish independence referendum – sparking the resignation of several senior people from the SNP ruling body.
Ms Sturgeon is under pressure to say if she knew about a possible arrest when she quit in February. Grilled about the police probe last month, Ms Sturgeon indicated she had not been interviewed by police.
Asked if she had heard about a police interview, she told Sky News: “No. I wouldn’t comment on any ongoing police investigation and I am not going to comment on this one.”
