The Northern line was once well-known as the Misery line for its persistent delays. Most of the problems were caused by signal failures or staff shortages, but occasionally something more unusual might undermine the service.
In the late 1940s, the line seems to have had a problem with dogs on the track, as these two incidents record.
2 October 1946, Daily Mail
At 5.55 last evening the driver of a Northern Line tube train pulled up with a jerk 200 yards short of London's Angel station. He saw ahead of him a large white dog which began to trot towards the station. The train followed slowly.
And for ten more stops the dog loped steadily ahead of the train, through Old-street, Moorgate, the Bank, London Bridge, Borough, the Elephant, Kennington, the Oval, Stockwell, and Clapham North.
Then, at Clapham Common, the train arrived first. The dog followed slowly.
It had stopped at the side of the tunnel, apparently for a well-earned breather.
On reaching the lights of Clapham Common the dog decided it had had enough, jumped up on to the platform as the train was pulling out ahead of it, whisked through the exit, up the escalator, and out into the street.
A London Transport official said last night: 'Trains on that section were slowed down by nearly half an hour afterwards'.
30 November 1948, Daily Herald
A black and white dog held up four miles of Tube trains in London last night.
It jumped on to the line at London Bridge (Northern Line) station and ran into the tunnel under the Thames. A Euston bound train, crowded with passengers, crawled behind.
At the Bank station and again at Moorgate, officials got on to the track, but the dog eluded them and ran on to the next tunnel.
The same thing happened at Old Street and Angel stations. Meanwhile the train — so packed that some passengers fainted — still crawled on behind, holding up following trains.
Near King's Cross, the dog touched the live rail and was killed. Then all trains resumed normal speed.
Sadly for headline writers, the Northern line goes neither to Barking nor the Isle of Dogs, though it will soon have an extension out to Battersea Dogs & Cats home.