As a result, dismayed by the monopoly position British Leyland now enjoyed,[2] by 1972 Scottish Bus Group had approached Seddon Atkinson; at the same time they were working with Ailsa, the Irvine-based Volvo truck importer, on a new type of double-deck underframe.

The frame did not continue aft of the rear axle-mounting,[5] collaboration with SBG's preferred supplier Walter Alexander Coachbuilders meant there was no worry about the body builder providing a strongly cantilevered rear overhang capable of supporting a capacious luggage boot, especially after Alexander's switch back (from 1967 to 1972) to aluminium alloy body framing.

The prototype (carrying a late body by Seddon's Pennine Coachcraft subsidiary) had a Self-Changing Gears semi-automatic gearbox, but production variants were initially to be fitted with a four-speed ZF synchromesh unit, coach versions having a higher ratio final drive allowing a 76 mph maximum speed, 56 mph being the designed maximum for bus versions, better acceleration and more flexible performance ensuing with the low ratio back axle.

In 1974, pleased with the initial batch, Eastern Scottish commissioned a longer version to carry the exclusive and luxurious Alexander M-Type coach body.

Orders for the new (third series) M-type coaches went to three chassis suppliers, Leyland, Seddon and Volvo, previously Western and Eastern Scottish had chosen a special version of the Bristol RE for M-type bodies but coach variants of the RE were axed earlier in 1974, the final 12-metre examples having gone to United Automobile Services earlier that year.

As circumstances turned out Eastern Scottish initially took four Leopards in the yellow and black colours of their previous M-types for almost a year before its Seddons were completed, then passing the Leylands on to the Alexander companies.

With the Volvo B58, Leyland Leopard and AEC Reliance supplying the premium-coach class, and with Bus and Car of Belgium, DAF and Mercedes-Benz also offering coaches (the former with a right-hand drive version of the Trailways (USA) coach), the Pennine 7 began to attract orders from private operators, all but one with Plaxton Supreme bodies, the first 12m example went to Smith of Wigan late in 1975 with an early Supreme III C50F body.

of Kingsbridge Devon got 53 seaters on 12m coaches, OK Motor Services were the only independent to take a Pennine 7 to bus grant specification an 11m Supreme II Express with 53 seats.

In late 1974 it was completed to full-PSV standards, fitted with 49 semi-coach seats and finished in National Bus Company leaf-green and white bus colours; it was licensed for the first time as UBU72N and sent to Crosville to help them to cover the remedial body and chassis work on the 100 Seddon Pennine RU owned by them, after the rebuilding work was finished it remained with Crosville and was retired after eleven years service, no further Seddons were purchased by NBC.

Morley's of Whittlesey found their three astonishingly economical, the high-geared one of the trio (RSD978R) averaging 21 miles per gallon, whilst the two-lower geared examples (NSJ19R & NSJ21R) still achieved 18mpg.

Leyland offered SBG alone a four-speed ZF manual option on Leopard which was taken between 1974 and 78 by Central, Western Scottish and the Alexander companies.