More than 2,000 tickets have already been booked for the UK's main Yom HaShoah commemoration, being held in Barnet on April 19.
Remember Together - We Are One also marks the 70th anniversary of the liberation of death camps and the event is being supported by well over 100 communal organisations. Tickets are free and the venue has the capacity to seat 5,000.
Board of Deputies president Vivian Wineman said: "This may be our last chance to commemorate the tragedy in the presence of living witnesses to it. I hope, therefore, that community members will make the extra effort to attend."
Yom HaShoah UK chair Neil Martin added: "In what many are calling 'the last of the big anniversaries', we are bringing together the largest gathering to remember the loss of six million and to pay tribute to the survivors and refugees for the remarkable contributions they have made to the Jewish community and wider UK society."
