So far as I know, there is no cure for fairy rings, unless there's some new solution I haven't heard about, but yours isn't exactly a ring is it? What's underneath there, looks like something's caused a hump in the grass, possibly the woody remains of something? If there is something, removing that might resolve the issue.

Thanks Bamboo, have noticed quite a few of them over both lawns and wonder how concerned I should be. Seems like a lot of work to remove them, a job for the Autumn maybe late September early October ???

Yep, or midwinter, if the ground's not frozen - I take it you think there's something underneath there as well then!

Need to ask the client, but don't think so , its in the spores the soil has to be removed along with the mushrooms.. ? No ???

Well that's an old method of trying to cure it, but I have to tell you its largely unsuccessful with a true fairy ring. One of my clients had one, and the husband had, some years before, excavated to a depth of 3 feet and 6 feet square, got rid of the soil and replaced with new - still got a fairy ring! But I should add that he's aware of why - says there used to be a large tree there, none of which is now visible, but I'd guess the underground roots rotting slowly were the cause.