The leaders of one the UK's most militant animal rights groups, which spearheaded a campaign targeting suppliers and customers of Huntingdon Life Sciences, were charged with conspiracy to blackmail yesterday.

Greg and Natasha Avery, who head Stop Huntingdon Animal Cruelty (Shac), are among 11 campaigners facing prosecution following co-ordinated police arrests across the UK this week - a move that has raised medical researchers' hopes that a significant blow will be dealt to extremists.