Frank Kelly first got his hands on Tube train signals as an apprentice in 1963. The kit he's still using today is older than him built in 1926.

When I first walked in to Finchley Central signal cabin it was the same as being beamed onto the bridge of the Starship Enterprise. FRANK KELLY, Service Operator, Transport for London

There would have been steam back then. This section of track dates back to 1863 and it was the first section of track [between Paddington and Farringdon] so it was steam trains - stream trains in the tunnel but they banned smoking on them. STEVE HOWE, Service Controller, Transport for London

The trains are now electric and these signals will be switched from mechanical to digital. Steve says, just like Frank, the kit still works perfectly.

The red levers are signal levers and the black ones point levers - red stop, go - black change track. It was ground-breaking when it was made. It's simple and it still works. You've got levers, you've got bars underneath that interlock to stop you putting one train on top of another. It's a simple principle but one that does still work. STEVE HOWE, Service Controller, Transport for London

The new system will be fitted in July meaning more trains will be able to pass along the track each hour, one every two minutes. It does mean Frank and his 92-year-old signalling system are retiring.