During a brainstorming session, Sid came up with the idea of a children's TV series based on the names of tube stations, which is how Underground Ernie was born.

Bakerloo is the detective of the Underground, while Hammersmith and City are two fast and furious twins who love quizzes and banking.

Over the course of the series, they are joined by their friends from across the world, such as the snooty Paris, gentle giant Moscow and fun-loving Brooklyn.

Alas, the excitable Jubilee can't keep a secret, and he and Ernie have to come up with a plan to get Sam 7 safely to the theatre.

[2] Some critics have pointed out the similarities between Underground Ernie and Thomas the Tank Engine and Friends, in that both series feature anthropomorphic locomotives.

Whilst acknowledging a similarity, the producers make it clear that this is very different from Thomas, and is very much based in the twenty first century.

Despite being underground metro trains, they often travel overground through the open countryside to various stations, including a seaside resort.

In November 2005, Halsall International Ltd. announced that they had secured the rights to produce merchandising linked to Underground Ernie [3][permanent dead link‍].

The show's theme song, performed by members of The Wonder Stuff under the name "HRB Music",[3] is called "The Importance of Being Ernie".

Co-creator John Deery has been seeking a £5.5 million investment in a bid to break the US market, with funds raised from that going towards making a second series.

According to creative director Adam Batham, the strained relationship between 3D Films and Joella Productions prevented another series from being made.