Oxygen masks were dropped down for the 89 passengers on board during the flight from Bahrain to the capital.
Cabin crew launched an emergency operation and the plane landed 40 minutes after the incident.
Everyone on board disembarked safely on Sunday and no injuries were reported.
A Gulf Air spokesperson said: “Gulf Air can confirm that flight GF003, an Airbus 330, flying from Bahrain to London on December 13 experienced technical issues that resulted in the airline’s experienced cockpit crew successfully executing an emergency descent and safely landing at Heathrow International.
“The aircraft landed without incident.”
Gulf Air is Bahrain’s largest airline and flies to 23 countries around Africa, Asia and Europe.
A Jordanian-American passenger banged on the cockpit and threatened to bring down the flight unless he was let inside. He was arrested when the plane landed after being guarded by two handball players.