Two men accused of being members of an illegal neo-Nazi group were urged to destroy evidence, a court has heard.
Connor Scothern and Garry Jack have denied being members of National Action (NA).
Birmingham Crown Court was told the pair received an email telling them to "throw away or burn any memorabilia" following police counter-terror raids.
Prosecutors said the message sent by another NA member showed they were part of the group.
Barnaby Jameson QC, prosecuting, said it was a "masterpiece of back-covering".
The message, headed "recent news", read: "I am sure you have all heard the news that four men have been arrested on the grounds that they are members of the terrorist organisation NA."
Advising several recipients to distance themselves from NA, the message added: "Delete any affiliations you have to the group.
"Throw away or burn any memorabilia you are holding on to. If anyone is caught breaking the NA proscription or advocating for NA or even holding any NA memorabilia they will be kicked from the group.
"Stay safe and be smart. They are watching the far right's every step now and if even one of us slips up it will cost all of us. This is an all for one and one for all situation."
Mr Jones and Mr Jack said they were "committed and unapologetic" members of NA but quit the organisation when it was banned, the court heard.
They are on trial alongside Alice Cutter, 22, and her partner Mark Jones, 24, both of Mulhalls Mill, Sowerby Bridge, West Yorkshire, who both deny being members of NA between December 2016 and September 2017.
Mr Jack, 23, from Heathland Avenue, Shard End, Birmingham, and Mr Scothern, 18, of Bagnall Avenue, Nottingham, are charged with belonging to the organisation between the same dates.
The trial continues.