Polemicist is a derogatory term for someone in Italy!
We could "what if" here forever, but in response to your question.
Canary wharf - hardly an ideal target or device (helicopter) for the job.
Where are you going to find an Apache available for the job at such short notice - realistically in the UK - the next day? Turn off the TXPDR (which crims know about ) and operate LL and primary radar is going to find them - yeah right.
As an aside to the above - harking back to 911 unfortunately - never could work out how someone who supposedly had done a few circuits in a Cessna 150 could operate an FMS or contend with the energy management required to get the aircraft to where they needed to be.
This was Bastille day in France pretty good chance everybody had the day off or was down on the Croisette in Cannes waiting for the fireworks or imbibing in the 4th pastis or so.
At the time coincidentally, I was standing where I could see both LFMD and this particular lockup. LFMD TWR will warn you about the location of this jail if you fly up that way and to remain well clear. This has been done before and the guards will normally open up without warning.
These are hardened crims - cunning as a $hithouse rat.
If cornered these people will take the next step - you (the pilot) are now currency in the whole deal as a hostage.
The guy that was extracted was doing time for murder. If he gets another 30 years on top of the 30 years he is doing whats the difference? He doesn't have anything to lose and all to gain.
I repeat - this isn't television!