Ahead of Brexit at 11pm on Friday, the Europhile campaigners will “thank the EU for what it’s done for the country”.
About 500 people are expected to attend, with the candlelit vigil taking place outside Oxford Town Hall at 6.45pm, followed by a panel discussion inside the hall.
Just before the 11pm departure time, there will be another vigil as they hold a lights ceremony outside using torches and phone lights. The lights, organisers said, will represent “hope for the future, which we think will be a European future”.
Colin Gordon, from Oxford for Europe, which is organising the event with the Oxford European Association and European Movement (Oxford Region), told Yahoo News UK: “It’s to mark the occasion, to regret the occasion and look back on EU membership in a sprit of celebration.
“We want to thank the EU for what it’s done for the country.”
Asked how they would respond to Leave supporters mocking the candlelit vigil, Mr Gordon said: “If they want to celebrate and be happy, let them celebrate.
“We will be expressing our own feelings in a measured way. It’s not going to be an angry occasion.
“It will be an occasion to look back and consider what we have lost.”
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Of the European Parliament’s ratification of Boris Johnson’s Withdrawal Agreement on Wednesday, which was the final legal hurdle it needed to clear, Mr Gordon added: “It’s painful but for the moment, we have to let it happen. What we do afterwards is what will matter.
“There won’t be a massive campaign to rejoin on Saturday morning - but we will be holding Johnson to account.”