rigid link between body and bogie, and oscillations created in the entire locomotive structure when the wheels hit pointwork or indifferent track made derailment a very real risk as the tyres on the wheels wore down. The D800s were subject to a maximum speed of and although D804 received modified bogies that allowed the top speed to be restored to in 1961, it took until 1963 before the modification was fully tested and all members of the class were modified. The "Bristolian" was decelerated by 5 minutes but an extra stop at Chippenham was inserted so that the drivers practically had no choice but to exceed to keep to time. All speed running ceased after autumn 1960, when BR's timetabling methodology as a whole changed towards making all inter-city services more regular interval with standardised train formations and more intermediate stops. No longer would crack expresses such as the "Bristolian" be given such priority: the hope (largely successful) was to increase locomotive and coaching stock productivity and also increase passenger numbers in an attempt to curb BR's still-increasing monetary losses. By 1964, the influx of both more powerful Class 52 Western diesel-hydraulics and Class 47 diesel-electrics drafted into the WR by BR's higher management meant that some D800s were spared for use on the Waterloo–Exeter route. At this time, the Western Region (formed upon Nationalisation in 1948 largely from the Great Western Railway) had just assumed control of this line west of Salisbury from the Southern Region of British Railways and conveniently used the "no more crack expresses" edict to get revenge on its pre-Nationalisation rival the Southern Railway by withdrawing altogether the SR's Atlantic Coast Express, which worked beyond Exeter, and replacing it with a semi-fast Waterloo–Exeter service hauled by D800s. The WR also took the opportunity to reduce its former rival's main line to single track for long stretches west of Salisbury and to sell off the "surplus" land – a move that is widely regretted today. The late 1960s saw a brief revival in the fortunes of the D800s. For a few months in late 1967 they moved on to the Paddington–Birmingham New Street route and then in early 1968 Paddington–Hereford. Rising traffic levels on the Paddington–Plymouth route meant the WR aspired to an hourly service interval for this route with standard 10 and 12 carriage trains. The maximum schedule was to be 4 hours 15 minutes