A man, aged in his 70s, has been arrested by police on suspicion of encouragement to commit arson.
Police have said that the arrest relates to a video he posted allegedly encouraging people to ‘burn MP’s offices.
Met Police added: “He was arrested in Southwark at around 01:45hrs on Sunday, 19 December.
“The arrest relates to a video posted online in which people were encouraged to burn down MPs’ offices.
“The man remains in custody at a central London police station.”
Although not named by police, it is believed that the man arrested was Piers Corbyn, brother of former labour leader, Jeremy Corbyn.
The video, that went viral on Saturday night, appeared to show the 74-year-campaigner criticising MPs who supported the Plan B measures.