Gangster-turned-activist Lakha Sidhana is suspected of playing a key role in the tractor rally mayhem unleashed by the farmers protesting against the Centre’s farm laws on Tuesday, the Delhi Police said. Lakhbir Singh, alias Lakha Sidhana, who has been protesting with several farmers at the Singhu border in Delhi since November, already has more than a dozen cases registered against him in Punjab including one under Gangster Act.