By his grim pleasure in telling me I knew he was not lying. A surge of uncontrollable anger sent my hand to my sword hilt. Only Maredudd’s gasp and his arm across my chest stopped me drawing it from its sheath.

Through a red mist I heard Maredudd ask, ‘How do you know this, Dai? It cannot be true. Sir Owen was no traitor. He was fighting for his king.’

‘A monk from the Leominster priory told me: Owen Tudor was captured by the Vaughans a mile from the battlefield and taken to Hereford. They said he was executed in retaliation for the deaths of Edward of York’s father and brother at Wakefield.’

‘They were killed in battle!’ I protested. ‘Vaughans – which Vaughans?’ I asked.

‘Roger Vaughan of Tretower and his men the monk said it was.’

Before that moment I had not considered myself a vengeful man but I became one in an instant as the name seared itself on my brain like a brand. I took my hand off my sword and stepped back from my squire’s restraint. ‘Let us go to the church, Maredudd,’ I said in as calm a tone as I could muster. ‘I have a vow to make.’

The little stone church on the seashore served the inhabitants of a number of farms scattered on the lower slopes that led up into the mountains of Gwynedd. Its churchyard contained only one fresh grave. I spent a few minutes offering prayers for Hywel’s soul; prayers unavoidably tainted by regret that he had accepted my annual purses and then betrayed my trust by turning his coat. It came to me that his action might have been in retaliation for me taking Jane as my mistress, which only made things worse.

I left Maredudd at the graveside and entered the church, shivering in the chill of an interior that the sun’s rays never reached in winter. It lacked the wall-art of English churches and was dim and stark but a beautifully carved crucifix adorned the bare altar and I knelt before it, removing my gauntlet and putting my hand on the cold stone table. My voice echoed around the pillars of the empty nave and up into the timbers of the roof.

‘I Jasper, Earl of Pembroke, swear by Almighty God that I shall not rest until the man responsible for the murder of my father, Owen Tudor, on the block at Hereford, is dead at my hand, and I name him as Roger Vaughan of Tretower.’