Td5 keeps stalling at low revs

Any help here will be very gratefully appreciated. After a long period of running off road in southern Spain, very dusty, the engine started to cut out at idle. The engine will re start immediately but will stall again at idle - sometimes.
Once on the move performance seems to be fine.????????????????

em... keep the revs up

replace the air filter.... do you still have EGR on?

Change the AIR FILTER !!!!!

The clue is in the words "very dusty".

Thanks guys, Ive changed it and it seems to be fine.