Not my find, but taken from Travelzoo weekly email:
Yes, it's real: For a limited time, Eurostar is offering two return tickets to Paris, Brussels or Lille for a total of just £58! That's half the usual lowest rate.
Departing from Ashford International to Paris or from Ebbsfleet International to either Paris, Brussels or Lille, you can travel to the continent until 31 August.
Youll need to book this offer before 31 May, and it's already selling incredibly quickly -- we found the best availability on midweek departures. Book your tickets at least 14 days prior to departure, but not more than 120 days prior to the return travel date.
Hope this helps! Click the link to take you to the page to book!