Members of a team of 27 lecturers and art workshop leaders who say that they were sacked by the National Gallery in London have spoken this weekend of the heartache behind their collective legal action against an institution they still love and thought of as “a second home”.

“It has been a difficult atmosphere at work for a while now,” said Karly Allen, 43, who has led many visitor sessions at the gallery, including a long and successful series of life-drawing classes. “Leaving has broken peoples’ hearts, really.”

The highly qualified group, most of whom have worked with visitors to the Trafalgar Square gallery for at least a decade, say they were told they were no longer needed in October last year, but were given no compensation or recognition of their long service. A small number of them were offered new work, for less money and on reduced terms. Last week the 27 learned their claim to have their employee status and rights recognised will be heard in full at a tribunal later this year.

“It is encouraging that the tribunal has allowed eight days to hear our case, which was unexpected. Now we have to fund the legal costs,” said Allen. “I’ve worked there for 18 years, so am a relative newcomer, as some of us have worked for more than 40 years. It has felt like a second home, so the process … has been really upsetting.”

Her former colleague, art historian and performer Richard Stemp, has worked at the gallery for 24 years and was one of those offered a new contract. Yet, he says, he cannot afford to take on the work. “No matter how very rewarding it has been as a job, the new terms are not acceptable,” he said. “We are generally appalled by what has happened.”

Stemp, 55, who has a Cambridge doctorate and lives in east London, is typical of a regular workforce who have a combined knowledge of the gallery’s collection that might well be considered a valuable national resource in its own terms. He feels expelled from the beloved landmark building in which he has happily run guided tours and classes for so long. “Sadly, I think I worked my last session on Tuesday,” said Stemp, whose book on the Italian renaissance was republished last week. “I will miss talking about the collection and sharing my enthusiasm for the paintings, and learning new things from the public reactions.”

A Monet exhibition in the National Gallery. “I will miss talking about the collection and sharing my enthusiasm for the paintings,” says one guide. Photograph: Guy Bell/Rex Shutterstock

Another former educator, Linda Bolton, 64, has led sessions for blind and partially sighted people, and with the elderly, as well as in schools, over 27 years of teaching and operating as the public face of the gallery. Even her basic guided tour, she said, “provided a way to communicate to the public at its widest, the international visitor paying a one-off visit and the regular attender, happy to engage repeatedly with the nation’s paintings”.

She particularly loved giving talks to school groups. “The community is enriched by its education programmes and we were enriched by their participation,” she said. “I feel privileged to have made a bit of a difference; to have made the National Gallery a place where people could find a voice. So many times a teacher would tell us, of the prime contributor in a session, that they usually didn’t say anything in class.”

Allen studied at Camberwell College of Arts, at the Ruskin School of Art, Oxford, and then for an art history MA at Soas in London. “We are all graduates or postgrads, and we each have areas we are particularly passionate about. For me, it is the drawing and the work of Piero della Francesca, Raphael, Velázquez and Caravaggio. I’ll miss the conversations with visitors, getting across the way that painting is really about what it is to be human.”

The 27 worked regularly, were issued security passes and ate in the staff canteen. “I have never had a period when I haven’t heard from the gallery. I took maternity leave, but could not call it that. The gallery refused to pay me statutory maternity pay, as well as denying us our other rights as employees. It is these sort of issues that need to be sorted out.”

I'll miss the conversations with visitors, getting across the way that painting is really about what it is to be human Karly Allen

The dismissed educators, Allen pointed out, only existed as a team because the gallery put them together, taxing them at source on the payroll, calling them in for training, annual reviews and strategy meetings.

This weekend the gallery emphasised that all the “freelance workers” had been consulted and that their individual claims “have arisen out of the gallery’s wish to change from offering ad hoc work to offering more secure employment, with additional pension and worker benefits” as part of wider plan to use digital technology to “widen our engagement”.

“The gallery is not yet in receipt of the details of each complaint, but believes that we have acted both lawfully and fairly,” it said.

The dispute follows recent high-profile claims made by “gig economy” workers in the private sector, including those against Uber and Pimlico Plumbers. Allen suspects their own case is just the tip of an arts-sector iceberg.

“This is bigger than just us, which is one of the reasons we want to proceed and have started a crowdfunding campaign for our legal costs,” she said. “The gallery has cast aside more than 500 years of collective experience, experience they have relied upon for the past 45 years.”

Karly Allen, 43, worked at the gallery for 18 years

“When we look at a painting we see ourselves reflected back, which is why it’s so rewarding to share the experience with groups of visitors. It offers us a sense of connection with other humans across time and space. It feels as if the paintings absorb all the conversations that happen in front of them, and our job is to fuel this communication between pictures and people.

“I’ll always remember the woman who approached me after a lecture where I had talked about Duccio’s The Virgin and Child with saints Dominic and Aurea to say, ‘I’ve been looking at this picture for over 50 years and I’ve never seen it quite like that before.’ I was only in my mid-twenties and felt so humbled; what a testament to the power of paintings to keep unfolding the more you look.”

Richard Stemp, 55, worked at the gallery for 24 years

“I can’t tell you how many times I’ve had a really mouthy kid in a group who just won’t stop talking – it’s not ideal because you want everyone to contribute. But then afterwards an astonished teacher asks, “How did you get that child to talk? They never say anything in class!”

“Just recently I had a group of big and sulky teenagers who looked like an art gallery was the last place they wanted to be. But one of them was being remarkably observant and very perceptive – way ahead of me – and made connections that no other student has made in the 24 years I’ve been there. After the talk the teacher come up to me, thanking me profusely, and told me that he was one of the most disruptive students in her class. That’s the power of art.”

Linda Bolton, 64, taught at the gallery for 27 years

“I clearly remember turning from my shopping trolley in Woolwich Tesco to look at a small child one day.

“Hello, do you remember me?” I had a stab. “From the National Gallery? What did we look at?”

“The Judgment of Paris and one about Bacchus and Ariadne on the island”

“You’ve got a good memory.”

“We did it later in school assembly. I was Bacchus.”

“Great! Have you been back there?”

“Yes. I took my uncle when he was looking after my sister and me. I told him all about all the paintings we looked at. The Greek and Roman myth ones specially.”

“I bet he was impressed, at your memory”

“I think he was. He’s taking me and my cousins there in half term.”

I said I hoped I’d see him there. I knew I probably wouldn’t. And in a sense it didn’t matter. Job done. And I was glad to have been part of the very big something. The something that brought art and stories to life, and gave ownership to being alive and engaged in public spaces.