Wow! Great video.
I see that a third Gnat will be joining the other two for next year. Folland Gnat XR991 (G-MOUR) has been moved from Delta Jets at Kemble to The Heritage Aircraft Trust at North Weald joining XS111 (G-TIMM) and XR5438 (G-RORI). XR991 is to be retained in its present yellow livery.
You wait for a Folland Gnat for ages, then three turn up at once!