Tuesday 4 October 2005 10.51pm
I'm sure a lot of the night flying helicopters are MPS ones. Not all of them have big "Police" markings on them (see http://www.met.police.uk/asu/
I don't think this link in this old thread is still active, but if I remember correctly it was an article about how the ASU had got themselves some shiny new helicopters so they were now able to provide full 24hr air coverage of London (previously they had only been able to provide dedicated air coverage at certain times of day). It certainly seemed to coincide with the increase in night flying helicopters in SE1 !