Unfortunately, Blastgard also specify that:
For confined and poorly vented compartments, leakage pressure, gas pressure and gas impulse may be estimated by assuming the net equivalent charge is reduced by 50%... Similarly, effective charge weight can be assumed to be reduced by 50% when calculating external overpressure and impulse if charges are placed in containers expected to shatter due to internal blast.
In other words, the effect of a BlastWrap chemical-sachet bin liner is equivalent to that of halving the explosive charge. Not really good enough, we'd submit. We put that point to RE:NEW's Spears.
"There's steel reinforcement," he said, adding that BlastGard have "helped in the development" of the proposed London bins, but that they contained "multiple technologies".
Unfortunately, a steel box can be a bit of a double-edged sword when it comes to confining explosions. In the case of a small device, whose effects might be derived mainly from flying shrapnel - on the general level of a hand grenade, a pipe bomb or an incendiary - it could be very effective.
In the case of a good big charge of high explosive (home-made or not) a steel box can actually enhance the shattering force of the explosion as it fails - and worse still, add fragmentation.
But a small bin - so as to prevent people getting much bang inside - combined with BlastGard suppressant and a heavy steel box could work fairly well. You could probably still cause a catastrophic failure by elaborate methods - filling it to the brim with blasting slurry or some other liquid explosive, maybe - but terrorists operating within the CCTV nexus of the City would struggle to achieve this sort of operation.
The one thing that really bothered us about the bomb-bin tech specs was that they are being kept secret. RE:NEW have consulted with the UK government's Centre for the Protection of National Infrastructure on it, said Spears, and the technical details are considered "so sensitive we don't even circulate them in the company".
"They don't want to talk in detail about the security features, for obvious reasons," he said.
We asked if that didn't pretty much imply that there was a vulnerability that terrorists could exploit.
"We don't want to make it any easier," said Spears.
Frankly, it seems fair to give Spears and RE:NEW the benefit of the doubt on the bombproofness of their bins, even given their security-through-obscurity approach. It's not as though bin bombing is that big a threat, after all, and they've plainly made some effort.
The solution adopted by less affluent London boroughs, with less restrictive ad-hoardings policies - so unable to sell binside media space - is transparent binbags attached to lampposts etc. This too is seen as an acceptable compromise between making life hard for bombers and reducing litter.
So what's worse? Twenty-four-seven ad-supported rolling financial news screens on every street corner, or transparent bags of rubbish and ad hoardings?
Would we, perhaps, sooner have ordinary bins back, and chance it that the odd one might explode? ®