Gnat, Valley, turning finals, wind blowing me towards the runway so tighten turn. Aircraft descending like one of Messrs Otis's finest. Me fresh out of ideas when voice in my ears says through gritted teeth "I have control". Man in the boot rolls wings level and pulls out of descent fairly near the ground. As we climb away, "If you had been on your own you would be f***ing well dead". Lesson well and truly learned and thank you Vic W for the subsequent 51 years