During the filming of Thunderbird 6 in 1967, the M40 motorway was being built and going to have central reservations installed throughout it. Executive producer and writer Gerry Anderson and director David Lane went to take a look at the motorway. The former suggested that the Tiger Moth could be flown under one of the bridges. Joan Hughes, who served as a ferry pilot in World War Two, would only be able to go under with the aircraft if she followed a stipulation by the Board of Trade - the Tiger Moth would be able to go under the bridge but providing the aircraft's wheels were in contact with the road. Furthermore, a Department of Transport official was on-site during filming so as to ensure the stipulation was adhered to.
On the morning of 21 May, Hughes taxied under the Bigmore Lane Bridge on three test runs. None of these passes had any visual impact. Hughes made another pass after this, but due to a crosswind and breeze which she thought would make her lose control of the plane if she attempted a landing, Hughes flew under without touching down, meaning that while she prioritised health and safety, she technically failed to adhere to the stipulation.
Ultimately, as a result of Hughes' actions, Century 21 were not allowed to film any more footage on the M40. She and production manager Norman Foster, who was supervising the filming of the Tiger Moth, would have to go to a hearing in March 1968 before the Aylesbury quarter sessions for the incident.
During March 1968, the court hearing commenced, and it lasted two and a half days. It took forty minutes for the jury to reach a verdict of not guilty for thirteen charges; Foster was faced with three of aiding and abetting, Hughes employers, Personal Plane Services, were faced with three charges of dangerous and low flying, and Hughes herself had to answer seven charges of dangerous flying respectively. On 20 March 1968, Hughes, Personal Plane Services, and Foster were acquitted.