The Holly Tree
There are a lot of pubs next to train stations in London, it's almost a requirement of city life to have a beer whilst waiting for the 13.03 to Staines or wherever you happen to be going.
Many pubs, especially those which have a more traditional decor, have pictures of steam trains or pre-Beeching stations.
Only one pub I've ever been to has a narrow guage train in its beer garden though, and that's the Holly Tree in Leytonstone.
What could be more entertaining for the pub-touring adult than a ride on a little choo choo? It's honestly a really nice idea and in this family-orientated part of the city I can imagine local children enjoy it too.