SWEET Caroline began its journey, tunnelling under Hillingdon and Ealing yesterday (27).

It’s the second boring machine launched by HS2, the high-speed rail link, and joins Sushila, which was switched on this month on the same West Ruislip site.

Named after 18th Century astronomer Caroline Herschel, the 2,000-ton machine will dig for 22 months, non-stop except for Christmas Day, towards Greenpark Way in Greenford. It will dig five miles of the twin-bore Northolt Tunnel.

Caroline will be operated by a crew of 15 people, working in shifts. An additional 25 will directly support the work on the surface.

The name ‘Caroline’ was put forward by pupils at Brentside Primary Academy in Kennedy Road, Hanwell.  

Once the tunnelling machines reach Greenpark Way, they will be dismantled and extracted from a 40m deep shaft.

Separately, two other massive boring machines will set off towards Greenpark Way from HS2’s Victoria Road site next year to build a further 3.4-mile twin-bore tunnel.

Combined, the quartet will build 8.4miles of twin-bored tunnels between West Ruislip and Old Oak Common.   

Another tunnel, from Old Oak Common to Euston, will complete HS2’s journey to its London terminus.

Spoil from the tunnels at West Ruislip will be used for creating embankments for the new railway, as well as new environmental habitats.

It will also be used to remodel West Ruislip golf course, which is closed during HS2 construction.