sentences:  However, following an invitation to Moscow in 1920, he was refused permission to return to Britain.He remained in Russia, became a member of the Bolshevik Party, took on the chairmanship of the "University reform commission" (1920–1921).On 6 January 1921 Rothstein was accredited as the Ambassador to Tehran and departed for the posting on 6 February after having had a discussion with Lenin.