Fenchurch Street was the first SimSig simulation ever developed. The software framework was still being created and development went down some blind alleys. The source of the simulation has been lost, but a few copies of the executable survived.
Clive Feather has spent some time reverse-engineering this executable to recreate the data for the simulation. And so we have SimSig Fenchurch Street Reborn!
This simulation covers Fenchurch St to Barking and slightly beyond and includes two timetables.