LONDON (Reuters) -British police said on Tuesday they had arrested a 21-year-old man on suspicion of arson after counter-terrorism officers launched an investigation into three fires, including one at a property owned by Prime Minister Keir Starmer. Police were called to reports of a fire in the early hours of Monday morning at the property in Kentish Town, Camden, north London, the area that Starmer represents in parliament. The man, arrested on suspicion of arson with intent to endanger life, remains in custody, police said.