The crew of flight VS025 decided to return to Heathrow rather than making the trans-Atlantic crossing, the airline said in a statement. Passengers were offered overnight accommodation.
Police said they were contacted Sunday evening and that no arrests have been made.
Lasers can cause a temporary loss of sight that persists even after the light is moved, the British Airline Pilots Association said. They also have the power to blind.
"This is not an isolated incident," said Jim McAuslan, the organization's general secretary.
"Aircraft are attacked with lasers at an alarming rate and with lasers with ever-increasing strength."
The organization wants British authorities to classify lasers as offensive weapons.
John Tyrer, a professor of optical instrumentation at Loughborough University, said it's not just airline pilots who are targets. He has been working with police officers facing riots in Northern Ireland to develop a strip on visors to counter such attacks.
"Laser attacks present a horrendous problem which is worsening with the easy availability of low-cost, high-power lasers," he said.
He said that it is possible to buy powerful lasers with a range of kilometers - rather than a few meters - particularly if the atmospheric conditions are right. Tyrer stressed that these more powerful lasers have no practical use.
"There are people that buy these things off the Internet which are shipped in typically from the Far East, which are very, very powerful lasers and have no use as a pointer," he said.
He said anyone hit with a laser could have watering eyes or a headache, though he cautioned that he had no direct knowledge of what the Virgin pilot might have suffered.
"This is not a prank," Tyrer said. "There are laws that say you can't do this."