Failed NCT on Tyres

Hi All,

My car failed the NCT due to having a "summer" tyre and "winter" tyre on the same axel. Has anyone ever heard of this before?

I don't know too much about cars so just wanted to confirm.

I had a nail in my tyre and brought it to a garage to fix but they said due to the size and angle of the nail they couldn't patch it and would have to replace the tyre.

It's only 6 months old and cost 280 so it annoying to have to buy another tyre when there is loads of thread depth on both.

Thanks