Those parts of Norfolk, Suffolk and Cambridgeshire bounded by:

On the North by the Lincolnshire boundary from Deeping Gate to the sea. On the South the Suffolk/Essex boundary to the A11, at Stump Cross. On the West the A11, A1304 to Newmarket, A142 to A14, A14 to A10 at Milton, A.10 to Stretham, A1123 to Huntingdon, A141 to B1043, the B1043 through Great and Little Stukely to Alconbury, the Old A1 to Norman Cross. A15, A605, A1139, A47 around Peterborough to the east, to A15 at Walton and A15 to Cambridgeshire/Lincolnshire boundary at Deeping Gate.