A stake in the kingdom - Nigel G. Tranter

Seventh son of the penurious Laird of Balfour, the fiercely ambitious David Beaton was determined to rise in the world - by whatever means available. Never one to be burdened by scruples, he cynically used the Church for his own ends to become one of the most able statesmen of his century and the real ruler of James V's Scotland.
An astute, courageous man, an accomplished fighter, fond of women, it was inevitable that Cardinal David Beaton would make many enemies. And that one day one of those embittered men would wreak a terrible revenge.

'Through his imaginative dialogue, he provides a voice for Scotland's heroes' Scotland on Sunday