Seb ran 1:42.33 for 800m, if my memory is correct, while studying for his final exams at Loughborough University. Seb was about age 22, if I recall correctly. That summer, Seb broke the world record for the mile (I think he ran under 3:49) and the 1500m world record (around 3:32). I remember reading about it in Runner's World magazine, which back then had fantastic articles about the great track men like Ovett, Coe, Wulhouter, Juantorena, Moorcroft, Salazar and Virgin, Walker, Dixon, Quax, Grant, Coghlan, Treacey, Rogers, Shorter, Brown, Malley, and many others.
Also, about that time, Seb ran in a national road relay (I think 4 miles, maybe it was 5) and ran the fastest time ever for the leg; faster than Mike McCleod and Brendan Foster, even, which was impressive since those two guys were distance specialists.
Peter "borrowed" his training approach from Coach Frank Horwill, who borrowed a lot from various coaches like Stampfl and Igloi.