Crossrail TBM Mary has broken through into the Woolwich station box, marking the halfway point in tunnelling works south of the river.
Mary, who began her stint in May, joins Sophia who is currently being prepared to continue tunnelling beneath the Thames to North Woolwich.
Sophia and Mary are constructing Crossrail’s the Thames tunnel which will created a link underneath the river between Plumstead and North Woolwich.
Since starting work in May, Mary has excavated 110,000 tonnes of material.
Gus Scott, project manager for Crossrail’s Thames Tunnel, said: “It’s great to know that we’re half way through our tunnelling in southeast London. Mary and Sophia have done a fantastic job so far, between them constructing a mile and a half of brand new tunnels from Plumstead to Woolwich.”