for the , but the "Cornish Riviera Express" would be retimed for 3 hours 45 minutes with stops at Taunton and Exeter only. The Class 52 Westerns could only cope with these timings on seven carriage trains. The answer was to assemble pairs of D800s and reinstate the multiple working equipment on them, allowing the pair to be controlled by one driver. This was done with D819/22–24/27–29/31/32 and D866–69 and the acceleration in schedules did bring a further 7% increase in traffic levels. It was not, however, without its problems: a fault on one locomotive in a multiple-unit pair effectively disabled both and one alone could not keep to the schedules. By 1969 only two services were booked for a pair of D800s, albeit losing a further 15 minutes off the schedule, and the timetable was largely recast into separate Torbay and Plymouth trains, instead of being split en route. This allowed the formations to revert to eight or nine carriages that a single Western could handle alone. From 4 October 1971 onwards, Class 33s were scheduled to take over from the Class 42s on Waterloo - Exeter services. However, even before this, they were being used as pilot locomotives on some services. Withdrawal Prejudice against hydraulic transmission among the heads of BR's engineering divisions led them to announce in 1967 that all the WR's diesel-hydraulics were non-standard and should be withdrawn as soon as possible. Compounding this were practical problems modernising the D800s: because of the scaled-down bodyshell, there was very little room inside for extra equipment. It was, for example, physically impossible to accommodate a compressor as well as an exhauster, so the locomotives were unable to haul newer designs of air-braked coaching stock. It also proved impractical to equip them with electric train heating (ETH) equipment for similar reasons, so they retained unreliable steam heat boilers to the end of their lives. It was intended to equip D870 with ETH, and to provide the necessary additional power, the engines were planned to be uprated by the fitment of charge-air coolers. However, no work was actually carried out other than the fitment of appropriate jumper cables on the locomotive ends. The pilot build trio were all withdrawn by early October 1968, these being followed by the Paxman engined D830 and three of the NBL Class 43s (840/48/63) in 1969 and then the mass withdrawals of 1971 which saw