V.I.Pompeius in Gaul 41.

V.VII.The Germans on the Lower Rhine 42.

The nature of the case as well as Caesar's express statement proves that the passages of Caesar to Britain were made from ports of the coast between Calais and Boulogne to the coast of Kent.
A more exact determination of the localities has often been attempted, but without success.

All that is recorded is, that on the first voyage the infantry embarked at one port, the cavalry at another distant from the former eight miles in an easterly direction (iv.

22, 23, 28), and that the second voyage was made from that one of those two ports which Caesar had found most convenient, the (otherwise not further mentioned) Portus Itius, distant from the British coast 30 (so according to the MSS.