Jessie is a 16" 0-6-0ST (identical to our Arthur). However, every time she has visited Quainton she has been masquerading as Thomas™ with side tanks fitted. Jessie is usually based at the Llangollen Railway in Wales. Jessie has been at Quainton for the Days Out With Thomas™ events in July 2016, Sept 2016, Christmas 2016, Easter 2017, July 2017, Sept 2017, 4 days of Christmas 2017, Easter 2018 and Christmas 2018.

After Christmas 2018 Jessie was put back to original condition as a saddle tank, so she will not be seen as Thomas after 2018. This was been completed, and Jessie reverted to a saddle tank configuration, in a black livery with rear cab wasp strips, relocating to a new home at the Pontypool and Blaenavon Railway. During 2023 - 2024 Jessie underwent a 10-year overhaul, before returning to Blaenavon. Subsquently she has been sold by her private owner, and is now owned by the Pontypool and Blaenavon Railway.