This ones a bit bigger than the last one. A mate is doing some fabrication work on a radar station for NATS, the air traffic control people.  It features 5 litre Mercedes diesel engine and it is probably powerful enough to power the whole of the circuit. 
Amazingly, it has been run for total of 70 hours in the last 25 years and is therefore virtually brand new.  Even more amazingly, it's going free provided you come along and collect it yourself.  You'll need a low loader to take it away, though.