The giant TBM nicknamed Phyllis arrived at the end of her 6.8km journey yesterday after being launched in May 2012.
Part of the boring machine will be left in the ground or “grouted in”.
Main contractor on the job is a BFK joint venture comprising BAM Nuttall, Ferrovial and Kier.
Phyllis and six other Crossrail tunnelling machines have collectively passed the 13 mile mark of their 26 mile marathon to build major new train tunnels under London.
Phyllis’ sister machine, Ada, is in the Holborn area and is due to complete tunnelling during the winter while another six machines will finish tunnelling next year.
During the coming weeks, Phyllis will be dismantled and her 130 metre long trailer system will be removed from the tunnel via the recently completed Fisher Street shaft.
Andy Mitchell, Crossrail Programme Director said: “Crossrail’s construction continues to move ahead at a significant pace.
“Crossrail has not only completed the first Crossrail tunnel under London but has reached the half-way point for our tunnelling machines with a phenomenal 13 miles of train tunnels constructed to-date.
“A further six tunnelling machines are currently hard at work constructing over 100 metres of new tunnel each day with major tunnelling due to complete next year.”