Just one of those things with a hand built car sometimes Aeroman

I'll get the heat shielding checked - I was queuing in traffic for a while right before switching off the engine - could just be that something got a little more toasty than it should have.
On the plus side I'd forgotten how much attention you get in a max - got videoed and photographed on the M1 and chased by a lady in a new Boxster.