I just had the amber exhaust gas emission warning light come on permanently (you know, the one you have to look up in the manual because it looks like a helicopter and is top left in the speedo!)

The only significant thing is I filled up with half a tank of diesel 30 miles previous so I hope its not another contaminated fuel saga (Waitrose, Swaffham, Norfolk).

Any ideas? Lambda sensor failure? DPF problem? the car is a May 07 SEL Estate 170PS DPF with 30,000 on the clock.