A week after far-right protesters stormed Britain’s largest socialist bookshop and destroyed books and magazines, crowds gathered on Saturday outside its doors in a show of solidarity.

A series of leftwing writers and poets addressed the audience, many saying that the attack on Bookmarks in London’s Bloomsbury by 12 people, including Ukip supporters, demonstrated how invigorated elements of the far right had become.

David Gilchrist, the shop manager, said: “It was an attack on the left and one that indicates their confidence, how emboldened they have become since the rise of Donald Trump and more recently the release of Tommy Robinson from prison.”

Among those gathered was Paul Holborow, who founded the Anti-Nazi league in 1977. He said he was starting to recognise the signs of far-right activity that his group was formed to challenge. “It [the attack] bears resemblance to what was happening in the late 1970s.”

Florien Hubner, 19, from Berlin had turned up to offer support because he had never believed such incidents were possible in London. “We have many attacks like this in Germany from Nazis but I thought it was better here. I was shocked when I found out,” he said.

Sophia Peach, 19, a Bookmarks volunteer, said one positive outcome was that the store had been busy ever since the attack, with queues of people bringing cakes and gifts, alongside thousands of supportive emails. “Every cloud has a silver lining – the response has been really uplifting.”

The author David Rosenberg, who read extracts from his book on the Battle of Cable Street, which chronicles how fascists were prevented from marching through east London in 1936, said that last week’s incident showed that the far right remain a “real threat”.

Michael Rosen, the former children’s laureate, wrote a special poem for Saturday’s solidarity gathering. It began: “It looks like we’ve got, yet another case of guys out rooting for the master race, invading a shop, being a bit of a pain, trying to make Britain great again.”