Twitter accounts based in Russia posted 45,000 tweets about Brexit within the space of 48 hours during last year's referendum on EU membership, an investigation commissioned by The Times has found.

Data scientists at the University of Swansea and University of California, Berkeley found that over 150,000 accounts based in Russia posted content relating to Brexit in the days leading up to voting day on June 23, 2016.
https://www.businessinsider.com/russia-used-twitter-accounts-to-meddle-in-brexit-investigation-shows-2017-11