Bertram is a narrow gauge engine who is nicknamed "the Old Warrior".
Bertram started working at the mines in 1899 alongside Atlas and Alfred, his number 4 until 1904, after Smudger was turned into a generator, Bertram was renumbered 2 before Stuart and Falcon arrived to work with him.
When the mines closed one by one in 1945, Bertram was lost and sent into a shed, he was rediscovered by Toby over fifty two years later after the mines re-opened.
In 2000, Bertram was sent to work on the Festiniog Railway, he became the number 3, Bertram worked until 2013, when he returned to Sodor, he was brought to the Skarloey Railway by Mr. Percival. The engines on the railway enjoyed his company and his stories, Bertram did his work without fuss and was always on time.
One morning, Bertram met Spencer pulling the Duke and Duchess of Boxford's Coach, Bertram introduced himself to him as Spencer was not amused to this and says that if he can beat him in a race in 64 seconds the next day he'll make a deal: Bertram, accepting this race huffs away back to the Skarloey Railway.
The next day, Bertram doesn't want to be late and have Spencer beat him in 64 seconds so he decides to rush as fast as he can. Spencer is waiting at the station for Bertram to arrive when Bertram is in such a hurry disaster strikes and he tumbles off the rails onto the ground below!
Spencer has a long laugh at Bertram's accident and says that he guesses he's the important engine and says to Bertram he couldn't believe he accepted his challenge, Bertram realizes he can't trust snooty engines and learns a valuable lesson from his mistake.
Bertram was still working on the railway weeks later. All of the engines liked Bertram and thought his stories were excellent except for one engine in particular and that was Duncan who was jealous and he didn't get why Bertram was so popular with the engines and how his stories were great wanting to play a prank on the engine.
A few hours later, Duncan comes to Boulder Mountain where Iron 'Arry is with a yellow cargo car just a few blocks away from Duncan. Duncan sees this and thinks it's a perfect prank for Bertram to fall into… however, his prank doesn't go exactly as well as he thought it would as he bumps into the cargo car himself, flies all over the railway and hits a signal by a station. Bertram comes over later and saves Duncan from his shame but Duncan still wants revenge…
The next day, Bertram had a delivery of trucks and he came up to a hill: Duncan is still determined to play a prank on Bertram and figures the best place to do it is on the top of the snowy hill. This prank backfires also as Duncan starts coming toward Bertram but what he didn't know is the track he was on is the track that an engine can fall off if they go on that track dangerously, Duncan doesn't know this and tumbles onto the ground below looking very silly indeed.
Later on, Madge rescues Duncan and takes him to meet Bertram and apologize: Duncan supposes he has no choice and says sorry to Bertram but Bertram says it's no problem and it's happy he helped a friend in need. However, Max and Monty come toward Duncan carelessly and bump Madge's flatbed which makes Duncan almost fall off the rails. Duncan says that he guesses he deserved this but Bertram knows that Duncan was just being Duncan.
Mighty Mac needed new brakes and Mac decided to get new brakes with Mighty but Mighty refused to get the brakes even though he was reminded what happened to James' incident with old wooden brakes a lot of times.
The engines set off to get the wooden brakes and Mac gets new brakes and little does he know that Mighty didn't get new brakes and kept his wooden brakes instead and went to sleep in the sheds.
Disaster lay ahead though when the slate cars are knocked off the rails and Mighty Mac races down and Mighty's old wooden brakes can't stop him in time that they hit a t-switch and come off the tracks.
Bertram is a nice engine at heart and is rewarded with the nickname "the Old Warrior" for being brave but is always ready to accept a challenge.
Bertram is painted dark brown with red lining and has two brown plaques on either side of his saddle tank with his name written in gold.
- Season 11: Around the Railyard in 64 Seconds, Big City Rumor (cameo), Station Situation, Duncan in the Dumps and Wooden Brakes
- Season 13: The Duke of Hazard, Rust or Bust (cameo), Go Boldly, Culdee (cameo), Ivo Hugh's Day at the Zoo and How Gator Stole Christmas (cameo)
- Season 14: Freddie at the Ready
- Season 15: The Maron Station Makeover (cameo)
He also appeared in a discussion.
- Bertram has a tender in the Thomas and Friends series but in Thomas the Tank Engine and Friends Wooden Railway Adventures, he is a tank engine instead; however, in Season 13 after an accident he is rebuilt as a tender engine.