A 15-year-old girl who was severely allergic to sesame died after eating a Pret a Manger sandwich that did not list the ingredient on its packaging, an inquest will hear this week.

Natasha Ednan-Laperouse was travelling with her father and a school friend from London to Nice when she collapsed during the British Airways flight in July 2016.

The inquest, which is expected to last five days, is likely to examine product-labelling laws and raise questions about whether gaps in regulation need to be tightened.

It will hear that, shortly before boarding the plane, the teenager had eaten an artichoke, olive and tapenade baguette bought from the main Pret a Manger shop in Terminal 5 at Heathrow airport.

She collapsed on the plane and, despite her father administering two doses of drugs to revive her using EpiPens, was declared dead later that day at the university hospital of Nice.

The coroner will hear evidence from the girl’s father Nadim, the millionaire founder of the Wow Toys company, as well as the Pret store manager on the day the girl bought the baguette, and the head of safety and compliance at the UK-based food chain, which has 500 stores worldwide and was sold in May to a German investment fund for £1.5bn. The British Airways captain and the flight crew will also give evidence.

“As a family now of three, my wife, son and I are still trying to adjust to life without our beloved girl,” said Ednan-Laperouse, who is being represented by Leigh Day solicitors.

“It’s a daily battle and the pain is indescribable. Everything we say and do is a reminder that she isn’t with us; her empty bedroom, school uniform hanging in her wardrobe, her holiday bag packed for her holiday in Nice has never been unpacked. We can’t bear to.”

Facebook Twitter Pinterest Pret a Manger sandwiches. Photograph: Alamy

It is believed the sesame was baked into the baguette rather than contained in seeds on its crust.

Sesame is one of 14 allergens that EU regulations stipulate must be listed in pre-packaged food products made off the premises.

But, as with other fast-food providers such as Itsu, Pod and Benugo that prepare their food every day in their own shop kitchens, Pret products do not have to be individually labelled with allergen or ingredient information. The “loophole” is supposed to free small, independent sandwich shops and cafe chains from onerous regulations.

Instead signs on shelves and at till points in Pret stores tell customers with allergies to speak to a manager who is trained to provide allergen advice. Information is also available in the company’s allergen guide, which is available both in stores and online.

It is understood that, before becoming aware of the case, Pret had started to improve the allergen information it provides to its customers, but the inquest will explore whether more should be done.

Legal experts suggest the hearing could trigger a series of civil actions, depending on the coroner’s findings.

The Observer understands that Pret has been asked to provide details of any other customers who have suffered allergic reactions to its products in the last two years.

The inquest will also examine the lifesaving measures taken by British Airways staff on board the flight, the training that they were given and the equipment they had for dealing with severe allergic reactions.

It is expected to examine whether the aircraft should have altered course to land at a closer airport – Lyon – and what advice the pilot sought from medical experts on the ground.

The role of French paramedics when the aircraft landed – and questions about whether their equipment, in particular a defibrillator, was functioning – is also expected to come under close scrutiny.

Pret’s use of labelling saw it come in for criticism earlier this year. In April, the Advertising Standards Authority censured the firm for claims it had made about its sandwiches using only natural ingredients.

The ASA said that adverts on Pret’s Facebook page and website, which claimed the chain made “proper sandwiches avoiding the obscure chemicals, additives and preservatives” used by other fast-food chains and that its products were “good, natural food”, were misleading.

The watchdog said: “We considered that because some of Pret a Manger’s foods contained E-numbers … those foods did not constitute ‘natural’ foods for the purposes of the [food labelling] guidance.”

This week’s inquest has similarities to a claim made against Pret in the US. In September 2015 David Matt went into anaphylactic shock after eating a sandwich at a Pret store in New York city. Matt, who is allergic to sesame, stated that the label did not list the allergen as one of the ingredients and filed a lawsuit against the chain.

But sesame is not classified in the US as one of eight major food allergens which have to be listed, and a court found in Pret’s favour.

“We were deeply saddened to hear about Natasha’s tragic death, and our heartfelt thoughts are with her family and friends,” a Pret spokesman said. “We take food allergies and how allergen information is provided to our customers extremely seriously. We will continue to do all that we can to assist the coroner’s inquest.”

In a statement, Natasha’s parents, said: “As a family of four, we had a very close relationship. Our home was quite noisy with laughter, joking and teasing. As a teenager Natasha was always open with us and would readily talk to us about any problems she may be experiencing and would ask us for our advice. She had a strong moral compass and often showed maturity beyond her years.

“Natasha was a popular girl at school; she was hard working and was due to take nine GCSEs in the following year.

“She had a great sense of humour and was known for her contagious laughter – she could reduce a whole room to tears of laughter in minutes. She was also gentle, brave and loyal and showed great kindness and courage on many occasions. You could not ask for a more wonderful daughter.

“She did her work experience in May 2016 with Matrix Chambers in London and was keen to pursue a career in law. She loved all animals and, for four years, she mucked out stables and rode horses every Saturday morning at Hampton Court’s Horse Rangers.

“She was also passionate about ice-skating and showed great potential and promise as a figure skater.

“She broke up from school on Friday 15 July 2016 and was so excited about the summer ahead. We were travelling to Nice for a four-day break with her best friend as a special treat. After this, she had a week planned at a youth Christian festival in Norfolk and then we had a two-week family holiday planned in Greece. It was going to be her best summer ever.

“More than 300 people attended her memorial service in December 2016, on what would have been her 16th birthday. There were heartbreaking stories from her friends, all of them recognising what a great friend she had been to them. Other friends sang songs of love and friendship, and there were many tears. Her closest friends still miss her every day and have found life very difficult to adjust to without her.”

​A British Airways spokesperson said: “We were very sorry to hear of the death of our customer, and our thoughts remain with her family.”