The closest parking is at N 52 10.229 E 000 10.902. There is a narrow entrance - take care. You can get to the cache from Wandlebury Country Park but please use the public footpath to avoid the golf course (about 0.8 miles).
The Via Devana was a Roman Road connecting Chester (Deva) with Colchester (Camulodunum). Along its route it connected with the better known Fosse Way and Ermine Street. The Romans used it as a military route so after they left Britain in 407AD the road fell into disuse. The length between Cambridge and Haverhill is one of the better preserved sections and now forms an excellent byway.
The coordinates for the cache are
N 52 (SIX).(SIX)(SIX)(SIX)
E 000 (FIVE+SIX-2).(FIVE-2)(SEVEN-1)(SIX-2)
You can check your answers for this puzzle on Geochecker.com.