'You're pompous and rude': Anti-monarchist protester in on-air spat on Jeremy Vine show

An anti-monarchist protester who was locked up for 16 hours during King Charles's coronation has been involved in an on-air spat with a guest on the Jeremy Vine show.

Graham Smith, of the campaign group Republic, cut short his interview on BBC Radio 2 on Tuesday after claiming he was hijacked on the live broadcast.

He was annoyed he had not been told he would be joined by politics professor Anthony Glees, who said he disagreed with Smith's anti-monarchy stance.

It came after the Met Police expressed “regret” over the arrests of Smith and five other demonstrators ahead of the King’s coronation on Saturday.

Read more: Coronation protests: Pictures capture the uncomfortable side of King Charles's big day

Republic chief executive Smith was speaking to Vine about his arrest when the host introduced the professor to the phone-in.

Prof Glees started by saying he agreed with quite a lot of what Smith had said about the police being in the wrong but added he totally disapproved of what his group Republic stood for.

Smith then interrupted after being told to hold on by Vine, saying: “No, I don’t want to because I was not told I was going to be on this interview with anyone else."

He added he didn’t know who Prof Glees was but he was already being “incredibly pompous” and “rude”.

After being accused by the professor of not wanting to have a discussion, Smith added he routinely debated the issue but wasn't in a mood after spending 16 hours in a prison cell, adding he was not going to take any “nonsense” from Glees.

After another exchange, Vine then told Smith to hold the line while he talked to Glees but when he came back to him he was gone.

Smith later explained the incident, tweeting: “I slightly lost my cool on Jeremy Vine this afternoon.

“I hadn’t been told there would be another guest and I’m not currently in the mood for pompous commentators.

“I’m also not in the mood to discuss whether someone’s 'right' to wave flags at a king justifies locking people up."

Watch: 'Mistakes made' with anti-monarchy arrests, says health minister

Vine later admitted the show had not notified Smith he would be joined by someone else, replying: "Sorry you weren't told about the other guest – our mistake.

"He ended up agreeing with 90% of what you said. Best wishes and thanks from us."

Police had initially said the anti-monarchy protesters were arrested because they had items that could be used to lock them to positions on the coronation route.

But Republic said the items were for securing placards.

The force later said an investigations team had examined the items and no further action would be taken.

Smith said police had apologised to him in person on Monday but added he planned to talk to lawyers about taking legal action.