Through publications and overseas family commissions they influenced narrow gauge railway construction in Russia, America and throughout the British Empire.
In 1825, Spooner took a lease of William Madocks' house Tan yr Allt Isaf at Tremadog where Elizabeth and Harriet were born and Caroline was accidentally shot dead by Matthew.
However, it is now accepted that it was George's son Robert who advised the promoters of the Festiniog Railway, based on Stephenson's evidence to the Parliamentary Committee in 1832.
These allowed the horses to ride back downhill after they had hauled trains of empty wagons from Porthmadog to the slate quarries.
[citation needed] As a boy, with his eldest brother James he had assisted his father in laying out the Ffestiniog Railway and subsequently during construction.
He held the position for thirty years and dominated Ffestiniog Railway management and engineering until his own health began to fail in 1887.
Spooner was faced with the seemingly intractable problem of a railway working to maximum capacity yet unable to cope with the volume of traffic on offer.
It was through George England that Spooner commissioned Robert Francis Fairlie to design and build 'Little Wonder' an articulated locomotive ideally suited to a relatively short, heavily curved and steeply graded narrow gauge line.
In 1879, George Percival was exiled to India (owing to the pregnancy of Eleanor Davies, one of the servants) where his career blossomed and he eventually became Locomotive Superintendent of the Indian State Railways.
The brass trackwork and the engine and rolling stock were all made in the FR works at Boston Lodge (where the surviving track is now stored).
In 1998, the Ffestiniog and the Welsh Highland Railway Heritage Groups together undertook the restoration of the Spooner Family Grave in Beddgelert Churchyard.
This consists of a large double plot with two carved slate memorial tops surrounded by iron railings, which had been specially made in the Ffestiniog Railway Boston Lodge works.
The restoration work, which involved heavy weed clearance, the cleaning of the stones, and the rust proofing and painting the railings, caught the attention of Cadw, resulting in the graves now being listed as grade 2 monuments.