This page
Airport Minimum connection times for several major airports around the world - Denver to London says 1hr 15 min,
CAVEATS:
1) The page lists no effective date
2) There are no exceptions listed; there are always exceptions and they can be longer or shorter so AA to BD might be 1hr AA to NZ 1hr 30 and everyone else 1hr 15.
3) MCT only applies if you travel on a through ticket. A ticket and a reservation are NOT the same.