Police ditch Operation Bunter label for Boris Johnson visit over fears PM would think they meant Billy Bunter

Police chiefs changed the name of their security plan for Boris Johnson's next visit to Scotland from "Operation Bunter", in case he thought they were comparing him to Billy Bunter, it has emerged.

Force insiders confirmed that they replaced the randomly selected codeword over concerns that it would "cause some sort of diplomatic incident" by offending the Prime Minister.

They were worried he would think they were comparing him to the fat English public schoolboy who featured in fictional stories from the early 1900s by Charles Hamilton.

Mr Johnson, who attended Eton, has previously admitted he has struggled with his weight and earlier this year pledged to cut out "late-night cheese" and take early-morning runs in an effort to shed some pounds.

The codename Operation Bunter was said to have been plucked from a list of approved words, in line with police procedure.

However, it is understood that Police Scotland chiefs did not spot the potential offence the name could cause until experienced officers pointed it out.

An insider told the Scottish Sun: "Several people pointed out the foolishness of calling it after a fat, posh, English public schoolboy, not least given the PM is known for being a bit portly."

Police Scotland are said to have settled on Operation Aeration as an alternative but the source added: "I'm not sure moving from Billy Bunter to a name that implies the PM is full of air is much improvement."

The Bunter stories were set in the fictitious English public school Greyfriars and were originally published in cartoon form in 1908 in the Magnet. The magazine ceased publication in 1940 but they were later published in a series of books.

Billy was nicknamed the "Fat Owl of The Remove" as he wore glasses and was extremely overweight, wearing too-tight checkered trousers. Despite often acting selfishly and foolishly, he remains a much-loved comic character.

A Police Scotland spokesman said: "Operational names are auto-generated by computer and can be changed if they are deemed to be inappropriate."