At the turn of the 1960s, declining passenger numbers essentially forced bus operators to seek major operational economies, and rapid introduction of 'one-man operation' was the order of the day.
Our neighbouring Swansea-based South Wales Transport Co set about converting many routes from crew-operated double-deck operation to single-deck OMO.
Always ardent AEC operators, the company introduced a substantial number of these 36ft AEC Reliances, which boasted an attractive cherry/primrose livery with copious amounts of Herzim polished aluminium mouldings thrown-in for good measure. Being 6MU2R models, they had the lively 8.2-litre AH505 engine driving through 4-speed semi-automatic gearboxes.
The Marshall 51-seat bodies featured forced-air ventilation and extra-width entrances for ease of passenger flow:

Brunswick-based 972 is seen above at the Pentrepoeth Road stance on Morriston Cross when only a few days old, in the charge of my old friend/colleague Eric "Paddy" Somers on the busy cross-city 90 service, which was an early convert to OMO.
Although this big-hearted native of the Emerald Isle didn't suffer fools gladly, he was a brilliant jovial character who could really handle a 36-footer confidently and safely. His passengers loved him too!
A truly evocative shot that perfectly captures the mood of British life during my early years in the bus industry - with not a chav in sight!
(BTW; this location is just around the corner from our Plomien's gaffe!)