Unable to edit sketch plane

Hi,

I have attached a part that has one sketch and a thin extrude in it, very basic part. I will probably be embarrassed at my stupidity when I find out what I did wrong but here goes I cannot edit the sketch plane.!!!??? I right click on it like I always would but the plane icon is not there. If i create another sketch then right click on it then i can edit the plane but not for the first one.

Could somebody have a look and see if you can find the problem.

Thanks

Ben

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