There are quite a few issues around this, but we'll do our best to summarise. The law says that no vehicle, other than an emergency vehicle, shall be fitted with a blue warning beacon or special warning lamp, or a device which resembles a blue warning beacon or a special warning lamp, whether the same is in working order or not. Additionally, 'fitted' includes lamps which are masked over and those without wiring. The law also says that, with certain exceptions, no motor vehicle shall be fitted with a bell, gong, siren or two-tone horn. So, legally, the best way to transport such vehicles is on a trailer.

We spoke to the Police Vehicle Enthusiast's Club, who offered the following practical advice: No blue lights (or flashing red lights) to be shown - they must be covered up and the fuse fully removed. The words 'police' and any police crest must be fully covered, which includes any police/stop lights on the car. Two-tone horns, bells and sirens must also be disconnected and the fuse removed. The Club is very helpful and can provide more practical advice on this - but the bottom line is if you're in any doubt don't take the risk.