Glynn was the original No. 1 engine on the North Western Railway and used to work on the Ffarquhar branch line with the other "coffee pots". By the time Thomas had arrived, Glynn was the only remaining one and he was left rusting on a siding at Ffarquhar station, with ivy growing all over him. After meeting with and realising Thomas was the new No. 1, Glynn asked him to look after the branch line and wear the number with pride.
Many years later, Glynn was accidentally rediscovered by Marion, who was working on clearing the line for constructing a new warehouse. Worried that Glynn might be scrapped, Thomas moved Glynn to a carriage shed. The following day, Thomas introduced Glynn to Sir Robert Norramby, who eagerly agreed to have Glynn restored and brought to The Estate Railway. Once Glynn was fully restored, he gave Sir Topham Hatt a ride up to Ulfstead Castle for the Earl's Christmas party.
Following the party, the Earl showed Glynn around the castle grounds and the dinosaur park. Worried that the Earl had a new favourite engine, Stephen challenged Glynn to a race to Knapford, with the loser having to leave the estate. The two engines raced on the main line, stalling Gordon and James, who were traveling behind them. Despite upsetting Sir Topham Hatt and delaying James and Gordon's trains, Glynn and Stephen became firm friends, and the Earl explained his plans to have them work together with his upcoming railway museum project.
Although Glynn is meant to be one of the "Coffee Pots" of Sir Topham Hatt's unique design, his basis is actually the Dorking Greystone vertical boiler locomotive of 1871 at the Beamish Museum.
Glynn is painted red all over and has gold lining. He has a grey steam space cap and funnel with a brass funnel top. He has brass control caps and a brass nameplate. His number is in yellow right under his nameplate. Because he was left sitting in sidings for a while, he was covered with rust, but the rust was dealt with after his overhaul.
- Pooh and his friends met Glynn in Pooh's Adventures of Thomas & Friends: The Adventure Begins.