Gammon joint help

I'm currently following this recipe and I'm up to the part where I let it sit in the liquid for 30 mins. When I left it, it was simmering. When I came back, it was boiling...stupid induction hobs. (I know I should've checked on it, but I sat down and got lazy lol)

So my question is, do I need to amend anything for the roasting part, like reduce the time or anything? I've never done a joint like this before so any tips appreciated!