10¼"
'Jack' was built in 2016 for the Delamont Miniature Railway near Killyleagh in Northern Ireland. An unusual tender locomotive, it's still with the railway today
'George' was built for the Poole Park Miniature Railway, and worked there very sucessfully, bringing steam (and passengers) back to this once busy railway. Then the local authority convinced itself 10.25" gauge was dangerous, closed it down, vowing on expert advice to reopen at 12.25", but it ended up being rebuilt at 10.25", although by that time toperator Chris Bullen and 'George' had long since departed to a new line at Honeybrook Farm near Wimborne. That venture subsequently failed and 'George' has disappeared - for now at least.
Phalaenopsis sounds as though it might a roman god of steely grit and power, but it's actually a genus of orchids containing about 70 species. All very fitting, because the locomotive has lived it's life at the Mortacombe Railway, Chilton Garden Centre near Didcot
'King Arthur' has spent its whole life on the 10.25" Rudyard Lake Railway, but was designed for easy conversion to 12.25" should the need ever arrise. It's one of the most powerful 10.25" steam engines, and probably the largest (ie tallest and widest) locomotive to run at this gauge.
'Pulborough' has had a very stable existence, at the South Downs Light Railway from new. Named after the local town in West Sussex
Bray Valley has had a long and complicated life. It was originally built as a 7.25" gauge locomitive for the Stirling family's proposed tourist railway on Exmoor, but after a last minute change to the much bigger 12.25" gauge, it was hastily widenedn and regauged 10 12.25". Beneath the skin, of course, it was still fundamentally a little engine, and not really powerful enough, so it was regauged back to 10.25" and sold to a private owner in Wales