HE was arguably one of the most important Scottish politicians of the 20th century yet only two portraits of him are known to exist, and the mystery of who painted Tom Johnston is now proving difficult to solve.

The portrait of Johnston, Scotland’s wartime Secretary of State, adorns the cover of Without Quarter, the updated biography by veteran journalist Russell Galbraith.

The National recently revealed that the book, quite uniquely, has two forewords, one by former Prime Minister Gordon Brown and the other by First Minister Nicola Sturgeon, both of them paying tribute to Johnston who played a huge part in establishing the National Health Service.

For the cover of the book, Galbraith did not use the normal picture of Johnston – a portrait that hangs in Bute House, the First Minister’s residence in Edinburgh – but selected the portrait of Johnston which was painted during his time as general manager of the City of Glasgow Friendly Society, now Scottish Friendly, the largest mutual life office in the country.

Galbraith said: “Scottish Friendly have the portrait in their possession, but the problem is that we just do not know who painted it.

“It’s a tremendous painting of Johnston and really captures the essence of the man, but in the book I have had to admit that we just don’t know who to credit for the portrait.

“There is one theory that it might be an early work of David Abercrombie Donaldson, who went on to become the Queen’s painter and Limner in Scotland, but no one can say for certain who did it and frankly I’m baffled.”

Calum Bennie, communications manager for Scottish Friendly, confirmed that the painting was done while Johnston was at the Friendly Society from which he retired in 1946, but said there was no record of the name of the painter held by the company.

He explained: “There is a signature of sorts on the painting but it’s impossible to make out what the name actually is.

“The painting is not in the best of condition and actually has a small tear in it, so we keep it under cover in the basement. Maybe if someone could restore it we could solve the mystery of who painted it.”

Galbraith added: “Can knowledgeable National readers help?”