Ed Sheeran says his recent High Court copyright case over one of his songs was not about money but honesty and standing up for what was right.

The singer-songwriter told BBC Two's Newsnight he did not have a choice but to defend his work in court.

To protect against future claims, Sheeran said he now films all of his songwriting sessions.

A judge ruled on Wednesday that Sheeran had not plagiarised the song Oh Why by Sami Chokri.

In their first interview following the verdict, Sheeran and his co-writer, Snow Patrol's John McDaid, told Newsnight of the "extraordinary strain" the case had exerted on them.

Describing the court case as long and unpleasant for all involved, Sheeran said "there was no other choice" but to fight the claim.

"You can get a judgement or you can have a settlement and [when] you know that you're in the right, then you can't settle just out of principle. You can't settle.

"Our royalties were frozen and we were given two options and we chose the option that was integral to us."

McDaid added: "In the last year, it got really heavy and it was consuming. The cost to our mental health and creativity was really tangible."

This is not Sheeran's first time in court for a copyright dispute.

In 2017, the 31-year-old settled a $20m copyright infringement case for his song Photograph, something he told Newsnight he now regrets doing.

When asked if he thought that settlement had led, in part, to his most recent case he said "the floodgates opened".

It also led to him reassessing his relationship with the song.

"I didn't play Photograph for ages after that. I just stopped playing it. I felt weird about it, it kind of made me feel dirty," he said.

And there have been lasting effects on the way he works.

To guard himself against any similar claims in the future, the Grammy award-winning singer began filming all of his creative writing sessions.

He said he did not apply this protective measure to collaborative writing sessions involving other artists such as the Shape of You writing sessions with McDaid and producer Steven McCutcheon.

But he said: "Now I just film everything, everything is on film.

"We've had claims coming through on the songs and we go, well here's the footage and you watch. You'll see there's nothing there."

And his experience of songwriting has been tainted: "There's the George Harrison point where he said he's scared to touch the piano because he might be touching someone else's note. There is definitely a feeling of that in the studio.

"I personally think the best feeling in the world is the euphoria around the first idea of writing a great song.

"That feeling has now turned into 'oh wait, let's stand back for a minute'. You find yourself in the moment, second-guessing yourself."

McDaid called for more open discussion between all members of the music industry rather than more litigation.

"I think there's obvious holes in the system at the moment. If I can go to a musicologist and get a report and take that report and they can freeze someone's income based on that... that's a problem.

"It creates a culture where it can be used as a threat and I think we need to be having conversations with societies, with managers, with artists, songwriters and say this isn't OK for anybody."

They both spoke of their relief that the years-long process had come to an end.

"I'm happy it's over. I'm happy we can move on and get back to writing songs," said Sheeran.