Past Master: Master of Gray trilogy 3

With the end of Elizabeth I's long reign in sight, Patrick, Master of
Gray, is determined that James VI should succeed to the English throne.
Nothing can be allowed to stand in his way - not even his own daughter's
happiness.

And so Mary Gray and her lover, Ludovick, Duke of Lennox, are to be
caught up in a savage game of power politics, shaped by personal
ambition and religious bigotry.

The third volume in the Master of Gray trilogy by master of Scottish
historical fiction Nigel Tranter.