A man has been arrested on suspicion of making racially-aggravated threats towards Gina Miller, the woman behind the Brexit legal challenge.
Met Police said a 55-year-old man from Swindon had been detained for making racially-aggravated malicious communications online to Ms Miller from November 3 onwards.
Mrs Miller, 51, says she has been subject to torrents of online abuse, death, rape and racist threats since taking the Government to court over Brexit.
She sparked legal wranglings after submitting that Theresa May required the consent of Parliament to invoke Article 50 and begin the Brexit process.
A Government appeal to the High Court ruling, which sided with Ms Miller, is currently underway at the Supreme Court.
The man, who has not been named, was released on bail.
Officers also issued a "cease and desist" notice on December 3 to a 38-year-old man from Fife, Scotland.