Thanks for that, Paul. You're right. The end of Ainsworth's book must have been fresh in my mind:

In the area before the castle she sees a ring of tall stakes. She knows well their purpose and counts them. They are thirteen in number. Thirteen wretched beings are to be burnt on the morrow. Not far from the stakes is an enormous pile of faggots.

But Peel and Southern point out:
England to its credit, alone among the countries of Western Europe, did not permit witches to be tortured; unless they had committed treason they were straightforwardly sentenced to be 'hanged until dead'. Scotland followed the continental example with torture and the stake, and the margin of many an old Scottish Court Book bears the melancholy record written in after trial 'Convicta et combusta'.