A Just Stop Oil protester delayed 4,000 plane passengers in a protest against the UK reaching the hottest temperature on record, a court heard.

Cambridge University music student Cressida Gethin, 22, scaled a gantry above the M25 near Heathrow on July 20 2022, the day after the UK recorded a temperature of over 40C for the first time.

As a result of the protest by the climate activist group, 3,923 British Airways customers were affected by cancellations and delays, said senior manager at British Airways, Edwin Hall, in a statement read to Isleworth Crown Court on Thursday.

Broadcaster and environmentalist Chris Packham, 62, told the west London court on Wednesday that he was stuck in the traffic for four to five hours during a trip from Hampshire to Surrey, where he was working on a BBC programme.

He told jurors he came to “sympathise” with the fact he was forced to think about climate change while he waited.

During her trial, Gethin, who has taken two years out of her university studies, said she aimed to “interrupt business as usual” and draw media attention to the “dire situation” represented by the temperature in Britain.

That day, news of the protest aired on Good Morning Britain before she had scaled the gantry, she said.

The defendant added that she did not realise she was so close to Heathrow and did not choose the location.

Reading her closing statement, the defendant, who was self-represented, told the jury: “You must use your judgement as human beings, who are aware of the context in which this action was taken – the deadly 40C heatwave, thousands of people dying of heatstroke.

“If your house had just burnt down, would four hours in traffic feel serious in comparison?

“If you were a climate refugee, forced out of your home country by heat, drought and social conflict, would missing a flight feel serious in comparison?

“In a vacuum, you could reasonably assume that someone stuck in a four hour traffic jam would be feeling very annoyed.

“But we are not in a vacuum – no one here can disagree that the climate crisis we’re in is dire; billions of refugees, starvation, mass suffering and death – this is coming to us all.

“There may well have been more people in the traffic jams who felt like Chris Packham – we heard from Mr Packham that he did not feel seriously annoyed when stuck in the traffic.”

Prosecutor Neil Griffin told the court that Gethin refused to come down despite police requests to do so and warnings she was causing disruption.

He said: “What she did prevented thousands of people from being able to freely use the M25 and the surrounding roads.

“It’s not for one individual to say I believe in this so I’m going to stop you from using this motorway, I’m going to make your life miserable for hours and hours and hours.”

The defendant denies one count of causing a public nuisance contrary to the Police, Crime, Sentencing and Courts Act 2022.

She does not dispute scaling the gantry but denies that it amounts to the charge.

The trial continues.