The future 33 102, D6513, propels a 4-TC EMU on a Weymouth - Waterloo service at  Wareham on the 20th January 1971. The Waterloo – Weymouth line was electrified as far as Bournemouth and services would be in the hands of high powered 4-REP EMUs at the London end coupled to a 4-TC set of unpowered trailer cars at the Weymouth end.  The 4-REP would pull the 4-TC to London and then propel it back as far as Bournemouth where a push-pull fitted Class 33 would take the 4-TC the rest of the way to Weymouth .  The 4-REP would be detached and go back to London or do local work around Bournemouth .  Waterloo-bound trains originating at Weymouth would comprise the 33/1 at the Weymouth end propelling the 4-TC as far as Bournemouth where it would reunite with a 4-REP and the 33/1 would be detached.
(Photo courtesy David Mant . Many thanks go to Nick Field for the detailed caption information.)