A tree surgeon has said "climate change anxiety" was one of the reasons he scaled up Big Ben in London.
Ben Atkinson climbed up the clock tower dressed as Boris Johnson before unfurling two large Extinction Rebellion flags on October 18 last year.
The 43-year-old appeared barefoot at Westminster Magistrates' Court on Wednesday charged with trespassing on a protected site, namely Elizabeth Tower at the Palace of Westminster.
It is alleged he ignored warning signs about entering the premises.
Atkinson pleaded not guilty to the charge, but said after the hearing that he climbed up the clock tower out of "environmental, political and personal necessity".
Asked what his defence to the charge would be at trial, the father-of-two said: "Necessity is the defence.
"The environmental and political necessity in that we are in a climate crisis, accelerated by anthropomorphic climate change.
"The second part is the personal necessity, insofar my day-to-day mental state is very uncomfortable. Finding purpose in my day-to-day actions while faced with this cliff edge looming in the future."
He said he was motivated to climb the clock tower out of "climate change anxiety".
Atkinson, of The Hermitage, Rydal, in Cumbria, was filmed scaling the structure wearing a blonde wig, suit jacket and tie in October.
He said he chose to wear a "lurid green" outfit and a "Boris Johnson wig" as he "didn't want to be shot".
"I had to make sure it was obvious that this was not a terrorist incident," he said.
Atkinson, who also runs a glamping business, said he remained up the tower for about three hours.
After hearing the case on Wednesday, chief magistrate Senior District Judge Emma Arbuthnot set a summary trial date for April 14 at Westminster Magistrates' Court.
