The other big factor to keep in mind is Concorde hourly fuel consumption at cruising subsonic speed (something below Mach 0.95) was pretty much disastrous as it

The other big factor to keep in mind is Concorde hourly fuel consumption at cruising subsonic speed (something below Mach 0.95) was pretty much disastrous as it was the same than at vmo (which was Mach 2.02). So the goal was always to go supersonic as quickly as possible as the fastest she went the better the mpg got...