This is an excerpt from a profile last update in 2018. The full profile can be found here: https://powerbase.info/index.php/Mark_Jenner An updated version of the profile will appear here after the hearings of HN15 and 'Alison'.
HN15 Mark Jenner, alias 'Mark Cassidy', was an undercover officer who was deployed against left wing groups in North London from 1995-2000. He had a long term relationship with a woman who uses the pseudonym 'Alison'. He worked as part of the Metropolitan Police's Special Demonstration Squad and much of his infiltration would have served under the supervision of its then head of operations HN10 Bob Lambert.
His targets were a number of groups based around the Colin Roach Centre, particularly union organising and anti-fascism. It is also believed that some of his work was to monitor groups and individuals who had potential sympathies with Irish republicanism.
He was publicly outed in 2011, and this reached national interest in 2013 when his former partner 'Alison' testified before the Home Affairs Select Committee accompanied by an expose in the Guardian. For many years, the Metropolitan Police have maintained the position of neither confirming or denying that he was deployed by them.