Just for reference, while the gripper certainly didn't feel as if had a lot of spare thrust capacity, it obviously did meet them -BCARs at the time, now subsumed into JARs/FARs. These require that in the landing configuration, (i.e. gear down and landing flap) the steady gradient of climb may not be less than 3.2 percent, with the engines at the power or thrust that is available 8 seconds after initiation of movement of the power or thrust controls from the minimum flight idle to the go-around power or thrust setting" and at a speed not more than Vref.
That 8 second spool up allowance plus the fact that 3.2% is not much of a climb gradient - a bit less than 500 fpm at 150 kts. - means that the transition to a climb after pushing the thrust levers to go-around seems to take an awful long time!