Hello,

We have a patch of lawn that has suddenly become covered in wild mint. We've returned after two months and it has almost completely taken over the lawn. It has happened very quickly. I don't recall even seeing it there before we left. The lawn was quite mossy prior to the arrival of the mint.

Can anyone recommend an effective eradication method?

If you don't mind using a herbicide, one containing 2-4-D will kill the broad leaf mint without killing the grass. Follow the label carefully.

How long have you lived there?
Looks like apple mint... and... as the grass was thin, it looks like some help.
I always did want a mint lawn... allowed to grow enough to flower and attract pollinators, you have the start of a wildlife garden.
I think you should try making tea.