The high powered EMU tractor units were classified 4-Rep (Restaurant EPB), the trailer units 3/4-TC (Trailer Control) and the push pull equipped diesel locomotives were converted from 19 of the Southern's native BRCW type 3 fleet (eventually to become designated class 33/1).

All TC cars were rebuilt from loco hauled Mk1 coaches, TSOs being the donor vehicles for the DTSOs (with the former toilet compartments being rebuilt as the driving cab), the TBSs being rebuilt from BSKs and the TFKs from FKs. Initially 28 4-TCs were converted and formed DTSO-TFK-TBSK-DTSO. Acknowledging that the TCs would not only be used with Reps on Bournemouth services three 3-TCs were also formed with there being no TFK in the unit. The idea behind this was that a loco plus 3-TC plus two 4-TC would fill the same platform space as a 12 car EMU formation. However when used on Bournemouth services in summer overcrowding regularly resulted so in 1974 the 3-TCs were augmented with newly converted TFKs to 4-TC and at the same time a further three 4-TCs were converted.

Driving control was via the SR 27 core multiple control cables and power for heating, motor generator and compressor sets was obtained from a 4-Rep or locomotive on standard heating jumper cables at underframe level. The TCs could not only work in multiple with 4-Reps and class 33s but also with class 73s, class 74s and compatible 1951/57/63 EMUs. It is known that some services were run with class 33 or 73 locos sandwiched between TCs. It is remembered from the late 1970s a regular up peak working of a class 33, TC and Vep formation. Although ageing memory can play tricks it is recalled that this formation was put together at Basingstoke combining an up Salisbury and an up Southampton line service to save a path into Waterloo.

Such was the versatility of the TC units that they were not only used on the Weymouth line, and they were also associated with Waterloo-Salisbury, Clapham Junction-Kensington Olympia and Reading-Portsmouth services.

When first introduced the TCs appeared in overall rail blue livery with small yellow warning panels and small aluminium BR arrows affixed below their side cab windows. The yellow warning panels were subsequently enlarged to cover the whole cab front. They were repainted during the early 1970s into Blue and Grey, losing their aluminium arrows in the process, the 1974 conversions emerging in blue and grey livery from new. The TCs survived in service long enough to receive Network SouthEast livery.

During the final days of Rep/TC service on the Weymouth line temporary formations such as 5-TCB (4-TC + Rep restaurant car) and 4-TCT (buffet compartment in middle of TFK) were put together to keep the service running during the withdrawal of Reps and until the introduction of sufficient class 442 units. The versatility of TCs ensured their survival longer than their sister Rep units. Two units were "restored" to overall rail blue, albeit a glossy version compared to the original semi-matt, as units N°410 and N°417 for NSE premier charter services. Eight vehicles culled from six sets to make up two complete units were sold to London Underground Limited early in 1992. These were fitted with bars over their drop-lights and repainted into Metropolitan line red/brown livery with blue/mauve/blue lining and gold numbering and were used for surface line excursions. Today one 4-TC unit, N°417, in overall rail blue livery survives and is owned by Rolltrack Ltd (along with their Crompton 33103) for spot hire. During August 1999 this combination (running without its TFK) was used briefly on Silverlink's Barking to Gospel Oak services until the arrival of lesser class 150 units.