They will doubtless have planned to schedule staff in from other airports (GLA/EDI/BRS/etc) ........ So LHR won't be the only place with longer queues. ........... Some mgmt will go on the desks too.
Two things worry me about this. The fact that the chaos will be nationwide means that the potential for illegal entries is increased, and as for management going on the desks, they're the bunch of bozos that caused all the problems previously and are probably less competent than the workers.
Much as I dislike the Israelis, I have enormous respect for the way they do things, and I'd get Mossad to do it. It would be done with surgical precision and not the least worry about upsetting people on grounds of political incorrectness.