British Airways is currently running a sale on Business Class fares from Canada to London for the summer season. Fares start at $2698r/t (+taxes &fees) for travel Jun 28 – Sep 3 and need to be booked by Jun 16.
Montreal $2698 r/t
Toronto $2698 r/t
Vancouver $3298 r/t
Calgary $3298 r/t
You can book this fare at BritishAirways.com