This is normal!
All non franchised Leyland Olympians come new with 11R22.5 tyres on all axles.
After network 26 in 1993, Citybus upgraded the front and mid axles of their existing
11M and 12M single door Leyland Olympians to 295/80R22.5.
But all two door 12M Leyland Olympians are using 295/80R22.5 on front and mid axles from new.