THE East Coast Mainline from York to London reopened today after a massive engineering scheme was completed on time.

But LNER is warning passengers that trains will be very busy, seats on most trains towards London King's Cross are now fully reserved and trains will be diverted via Lincoln because further work is needed at Newark today.

A spokeswoman tweeted: "Thank you to the team at @networkrail from all of us at @LNER for working in the heat throughout the weekend to uncross King’s Cross.

"It’s been more than 20 years since anything like has been attempted, and the weather doesn’t make it easy. Huge project, well done team."

Managing director David Horne tweeted that more than 50 per cent of the company's London services would not be not running as work on a route upgrade continued today.

The work at Kings Cross has in included a switchover of signalling on the route north of Alexandra Palace to Sandy to York's high tech signalling centre.