The 0-6-2 wheel arrangement was common on the South Wales railways absorbed by the GWR in 1923. The 55XX class was urgently introduced as a standard replacement for many of the absorbed engines, which their previous owners had allowed to become very run-down. Their work in the Welsh Valleys needed locomotives with high adhesion rather than speed, so weight was not wasted by being spread over small non-driven wheels.
The need for 200 of these engines was so urgent that some were, unusually, built for the GWR by private contractors. All were completed by October 1928, when the last twenty, which included 6697, were received from Armstrong Whitworth of Newcastle (Works No 985).
Purchased by the by the Bristol Group of the Society from Croes Newydd (Wrexham) depot in 1966, where with No. 5605 it had become the last of the class in service, 6697 went to the Society's Ashchurch depot, being transferred to Didcot in 1970. The engine ran at Didcot until the late 70s when a flue tube collapsed when the loco was running on the main demonstration line. The locomotive it is now on static display.
She has recently been cosmetically restored in an unlined green livery with the GWR in unshaded lettering.