Unmarked police persons

In Ringwood (Hampshire, UK) I don't think I've seen an unmarked police car in ten years of living there. On the M3 up to London I would see, say, one a month - usually Volvos or BMWs.

Here in the big city I see them almost daily, sometimes several in high speed convoy all with the sirens going and the cunningly concealed lights flashing. Mostly dark blue and dark green Vauxhalls, although I did see an MPV the other week (I think it was a Xsara).

Yesterday I saw a novelty, an unmarked Golf burning along Southwark street at speed. The disguise further enhanced by the cunning ploy of putting an attractive female police person in a white polo neck behind the wheel. Had they been in normal cruise mode they would have been indistinguishable from any other happy DINKY couple.