A fatal mistake claimed the lives of a mother and daughter who died from carbon monoxide poisoning in a burger hut, a coroner has concluded.

The tragic error was revealed today at an inquest into the deaths of Leah Churchill, 50, and her 17-year-old daughter Brooke Wanstall.

They had gone to the Meet ‘n’ Greet snack wagon parked off the Old Thanet Way at Whitstable on the night of February 13 this year to decorate it with balloons and banners.

It was meant to be a 26th birthday surprise for Leah’s son Tyla when he arrived to open up for business the following day.

But the inquest heard they had started up a petrol generator – for either lighting or heat – which led to them being quickly overcome with fumes.

So instead of a happy scene, Tyla, who owned the wagon, made the horrific and haunting discovery of the lifeless bodies of his mum and sister. A birthday card had been left on the side.

A toxicology test revealed the pair had fatal levels of carbon monoxide in their system.

The inquest heard how Tyla, of Whitstable Road, Faversham, rang 999 and called emergency services to the scene but both his mother and sister could not be saved.

In a statement to the hearing, Detective Sergeant Zak Foote, who investigated the scene, confirmed there was no third-party involvement.

He said it appeared that “one or the other” had started the petrol generator, which was in an enclosed space, “unaware that they would be overcome by carbon monoxide”.

DS Foote said he did not believe it was the intention of Leah or Brooke to take their own lives – and concluded their deaths had been accidental.

Assistant coroner Catherine Wood said it was not a health and safety issue as neither of them were at work at the time of the tragedy.

She said: “My only conclusion is that their deaths were accidental – most likely due to the generator having been turned on in an enclosed space”.

None of the family were in attendance at today’s hearing.

The Valentine’s Day tragedy sparked an outpouring of grief and sorrow with Tyla issuing a warning over the dangers of carbon monoxide poisoning.

Speaking later the same day, he said: “They were decking the van out inside in balloons and bunting as a birthday surprise for me, like my mum would do at home every year.

"I didn't even know they were going down there but she must have started the petrol generator for power and to keep warm without realising the danger.”

Tyla said the generator was used outside the van during working hours but kept inside overnight for security reasons.

He had arrived at the wagon at about 8am to start work and was surprised to see his mum's car parked up outside.

"I opened the van door and and saw my mum and sister and for an instant thought they had fallen asleep," he recalled.

"I smelt fumes but it just didn't register straight away, but it became obvious they were both dead.

"I called the police and ambulance but it was the firefighters who told me it was likely carbon monoxide poisoning.

"It's heartbreaking to think they spent their last few moments just trying to put a smile on my face.

"Mum made a fatal mistake and we don't want this to happen to anyone else.

"Be aware of this thing, people. If you haven’t got a carbon monoxide alarm go and get one. It is a serious killer.”

The day after the tragedy, hundreds of friends, family and sympathisers gathered on the beach at Herne Bay for an emotional mass balloon release in memory of the mum and daughter.

Speaking at the gathering, the 26-year-old fought back tears as he embraced those who had travelled to pay their respects to his mum and "beautiful baby sister".

"We're overwhelmed and blown away by the huge support and kindness we've been shown,” he said. “Quite honestly, it's kept us going when we're all in a very dark place."

There were emotional scenes as music loved by the mum and daughter was played, with the crowd toasting Leah's life with her favourite drink, vodka.

Two appeals to help with the cost of their joint funerals also raised almost £20,000.

Leah, 50, lived in Wife of Bath Hill on the London Road Estate in Canterbury and was a mum of four, leaving behind another daughter, Ocean, 23, and son Sonny, 12.

"She was so kind and would do anything for anyone," said Tyla, who recently had a baby boy with his partner Beth.

"She would take a homeless man in off the streets if she was allowed. Brooke was just a live-wire with a huge personality.

"Mum worked all over the place, mostly in hospitality, and used to run the Share and Coulter pub in Greenhill.

"She was helping me in the burger van a couple of days a week."

Brooke, of College Gardens, Westgate-on-Sea, had just left Archbishop's School in Canterbury after completing her GCSEs.

"She had her whole life in front of her," he said.

"She did really well in her grades and had just started work as a carer, which she was really enjoying. She was also due to take her driving test next week."

Brooke's sister, Ocean, added: "She tried working in the van a couple of times but that definitely wasn't for her.

"Working as a carer was what put the spring in her step and the only thing she wanted to do."

Tyla, who also works as a drum and bass MC, said the whole family was left reeling from the tragedy.