Thanks Mike!
In that case the only advantage to using two separate cards is if one with a discounted card triggers the higher daily peak cap by travelling during the morning peak as the first trip (so doesn’t benefit from 1/3 off) but then subsequently only uses buses the rest of the day?
Tube Z1 (Peak from 2025) 2.90 (triggers higher daily cap)
Bus 1.75
etc…
capping at the full-rate future 8.90 Z1-Z2 daily cap.
Whereas a separate cap via either Contactless or back-office Oyster processing would be 2.90 + 5.25 = 8.15.
So in short on days like these where I do travel the morning peak the full rate standard blue Oyster would be better whereas on days I travel after 9:30 the discounted Oyster card would be better!