Political and women's rights activist Dr Shola Mos-Shogbamimu shared a chilling death threat from a neo-Nazi group which threatened to kill her and her family.
Dr Mos-Shogbamimu said the twisted threat was posted through her front door in London this week telling her she was on a "kill list" and would be "executed".
The sender claimed to be from National Action, a UK-based right-wing extremist terrorist organisation founded in 2013.
The murder threat was referred to as an "execution" and the letter began by saying "we are watching you" and continued: "Shola you are a constant troublemaker and liar who appears on television frequently.
"We have placed you on our kill list and intend to kill you, your children and your husband.
"You have gone too far and it is time for you to pay the price. We are looking forward to seeing your blood spill."
The letter goes on to include a string of appalling racist abuse - much of it too graphic to republish.
A lawyer and academic, Dr Mos-Shogbamimu often comments in the media on women's rights, law, politics, diversity, inequality and exclusion.
The letter said she clearly "belongs in Africa" and suggested she left the UK as soon as possible before she "received her punishment".
Broadcaster India Willougby claimed she also received a similar letter which was delivered to her accountant. Writing on Twitter, she said: "My accountant just called. He’s received a letter today - hand delivered - no stamp.
"Threatening to kill me. Because I’m trans.
"Full of graphic detail about what they are going to do. Passed on to the police.
"This is what Brit Media, the GC movement and the Gov have done."
Dr Mos-Shogbamimu received an outpouring of support online from people condemning "such hate and racism" and urged her to contact the police.
She also revealed her phone has been targeted, adding: "As I pick up, the caller drops. Ignored but it happened quite a number of times recently that I felt irked enough to mention it to my husband that it was weird/annoying but I didn’t dwell on it."
Police confirmed counter terror officers were now investigating the case, adding: "We are aware of letters sent to two people which contain vile racist and transphobic language, and threats.
"The letters are said to be from National Action London Cell.
"We are taking this matter seriously and an investigation is under way.
"Due to the nature of the letters and the potential involvement of a proscribed group, the Met's Counter Terrorism Command is leading the investigation.
"We were first made aware of the letters as a result of Twitter posts on Monday, 20 February.
"Officers have contacted the victims to request statements and to offer our full support.
"No arrest has been made at this stage and enquiries continue.
"If you have received a letter, or you have information that could help officers identify the senders of these letters, please call 0800 789 321."
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