A man was arrested on suspicion of common assault after an egg was believed to have been thrown in the direction of Britain's King Charles during a walkabout on Tuesday.
The alleged assault took place while Charles, 74, who came to the throne in September after the death of his mother Queen Elizabeth, was visiting Luton, northwest of London.
A police spokesperson confirmed a man in his 20s had been arrested in Luton's St George’s Square and was in custody for questioning.
Last month, a man was detained by police after eggs were thrown at Charles and Camilla, his wife and the queen consort, as they carried out an engagement in northern England.
The latest incident comes as the royal family braces itself for the release of a Netflix documentary series on Thursday about the king's younger son Prince Harry and his wife Meghan, and their latest expected criticism of the royal household.
UK PM Starmer says he will resign
Temperatures to exceed 40C in European heatwave as three die in France
US, Iran conclude high-level talks in Switzerland, mediators say
Philippines probes school shooting that killed 3, wounded 7
Moscow shoots down more than 80 drones; Russian attacks kill six in Ukraine
