But as a silver lining, from what I see, the public will be extremely glad to see someone in MTP acting as security rather than someone in a G4S uniform.
I disagree. I would rather see less security. The fact that we feel we need to hold QRA at a nearby airfield, have GBAD on tower blocks, and have airport-style security (complete with queues, 100ml liquids restriction so you have to buy your drinks at the sponsors' concessions inside, and the whole take-your-belt-off rigmarole) tells me something is wrong with our attitude to risk. In days gone by, even in the IRA era, this would have been done with some old-fashioned common-sense policing, some intelligence-led behind-the-scenes work and a bit of un-PC "profiling" of likely offenders (all of which, by the way, has worked very well for El Al over the years).
All this is a sign that our security policy is failing - the point of our overseas expeditions was supposed to be making us more secure at home, not needing to go through a full search to get into a sports event... so I would rather see some police, a small number of contractors, but no forces personnel on duty. In any case the Olympics is a crap target for a terrorist outrage - with so many nationalities around, the terrorists risk pissing off a random selection of countries, some of whom might actually be their friends. Only targeted Munich-style outrages would avoid that risk - and we haven't needed metal detectors at the Games for the last 40 years to prevent a repeat.