1944, with 150 octane high boost works!
No engine broke down!
http://www.spitfireperformance.com/no1_25lbs.jpg
http://www.spitfireperformance.com/25lbs_approval.jpg
http://www.spitfireperformance.com/no165_25lbs.jpg
http://www.spitfireperformance.com/adgbs29867g.gif
http://www.spitfireperformance.com/2taf150_112044.gif