In 2017, what names were given to the machines used to extend the Northern line on the London Underground?

In 2017, London school children chose the names Amy and Helen for the 100 metre-long (328 ft) machines that would dig a pair of two-mile (3.2 km) tunnels to extend the Northern line from Kennington to Battersea Power Station. According to tradition, the 650-tonne (716.502 US tons) tunnel boring machines could not be used until they were named. Helen was chosen in honour of the first British astronaut, Helen Sharman (born 1963), and Amy for the British aviation pioneer, Amy Johnson (1903-1941), the first female pilot to fly solo from Britain to Australia.

The £1.2 billion ($1,611,600,000 USD) project aimed to open an underground station at Battersea Power Station and at Nine Elms, but due to COVID-19, the opening was delayed until 2021. The Mayor of London Sadiq Khan said the expansion would “be a real boost to south London” and “provide thousands of homes and jobs for Londoners”.

The London Underground managing director Mark Wild said: "This is a historic moment ... as we prepare to start tunnelling to create the first extension to our iconic network for nearly two decades." The last major expansion of the London Underground occurred during the 1990s when the Jubilee line was expanded to serve between Green Park Stratford.

The Northern line is a London Underground line that runs from north to south London. It is printed in black on the London Tube map.