Ikea battery Christmas LEDs. They were about sixpence just after the event. Blue and flashy, IIRC.

Bloke was a complete cock, obv.

(Two Astra drivers, one minging bint in a BMW, a builder's van and the utter cockwit of a hairdryer pilot who decided to overtake while I was signalling to turn right. If it had stopped, I'd have put my kryptolock through its sodding helmet.)