Three minutes to start up and reach Take Off RPM.....not a rush job in modern Twins with FADEC's.
As the Pilot had flown the aircraft on several sectors that day already....there is no requirement for a full run-up systems checks.
If the radios and and nav systems had been pre-tuned and set up for the intended flight....it would just be a matter of turning them on.
To make a point about "time"....I once worked a job where we had to be airborne within two minutes of the Alert Klaxon sounding....and that included up to a fifty yard dash to the helicopter.
That is rushed.....sitting in the aircraft and strapped in and ready to hit the Battery Switch....three minutes is not.
But that was probably in the military. Many of us have done scramble type jobs. This was not, it was a passenger carrying flight into London Stansted. I will agree to disagree with you on the 3 minutes from start to airborne. But 7 minutes for an aircraft that had been shutdown and unattended for 3.5 hours seems quick to me.