This unbelievable image was tweeted by @FirstCC this afternoon...
According to FCC the driver of the train in the picture, which was not in passenger service, 'did them proud' by managing to stop short of the obstruction on the line.
According to @NetworkRail:
At 10:09, a train driver reported that water was flowing from the roof of the Moorgate Tunnel - between Old Street and Essex Road stations. Lines were immediately blocked and our response teams were sent to site.FCC also confirmed by Twitter that the piling drills are 'not railway related'.
At 11.05 our staff boarded a special empty train from Moorgate to investigate the problem. As the train approached the area at low speed, two large piling drills - which were being used above ground by a building contractor - penetrated the skin of the tunnel.
Repairs to the tunnel are ongoing but the line - which is normally closed at weekends - is expected to reopen in time for services on Monday morning.
It is believed that ground level drilling works at 'a private construction site' resulted in the breach to the tunnel wall.
Hopefully someone at said construction site will soon be helping the BTP with their inquiries...
UPDATE: Oh dear All Foundations, what have you done!