Some memes misspell the driver's last name as "Gunton," but the story is otherwise accurate.
On Dec. 30, 1952, a London city bus found itself in a precarious position: driving over the Tower Bridge as it opened to allow passage of a boat below. Today, the story is popular in meme form:
All the details included in this popular meme are true, as they were recorded contemporaneously in news reports. That incident was covered in a Dec. 31, 1952 Daily Mail Article:
TOWER BRIDGE OPENED AS BUS WAS CROSSING: INQUIRY TODAY
AN INQUIRY was being held today into the opening of Tower Bridge as a bus was crossing it last night. The bridge opened as the bus was in the centre of the two sections. The driver carried on and the bus fell about three or four feet from one half of the bridge to the other. Of the 20 people on board. 13 were injured. Three were detained in hospital.
The main question people were asking today was "Why did it happen?" When the bridge is being opened, a warning is given by red traffic lights and the ringing of a handbell by a bridge operator. The bus driver, Albert Gunter … said that the traffic lights were green as he drove across the bridge. He did not see or hear any danger signal.
A City Police inspector said that the usual warning signals were given. The superintendent engineer of the bridge said, "The bus came unnoticed onto the bridge as it was just on the move. It had sufficient speed to bridge the gap, but the rear wheels must have fallen with quite a jolt."
A relief man was operating the bridge at the time. An official of the City of London Corporation committee who control Tower Bridge, said today, "The committee will have a report made to them on the incident and will consider whether any further steps should be taken."
That report appeared to have exonerated Gunter, who was hailed a hero in the press just a few months later. As reported in the Evening Telegraph in April 1953, Gunter was awarded both vacation time, money, and other gifts for his actions:
CITY GIFT TO HERO
WITHOUT pretending that he wants the same experience again, Driver Albert Gunter, of London Transport, is thankful for the benefits that have resulted from his presence of mind last December. He is the man whose No. 78 bus was caught on a rising arm of Tower Bridge. His prompt action saved nine lives; won him a £10 reward from his employers and £35 from the City Corporation, who run Tower Bridge.
Today Gunter tells me more good news. In June he and his family will take a week's free holiday at Bournemouth hotel — the first holiday for five years. His son and daughter, aged eight and 14, are invited to the Lord Mayor's children' party in November.
Because this event was recorded in multiple media reports at the time it happened, and because those media reports verify the details in popular memes about the incident, the claim is "True."