A severely disabled boy is suing a theme park for failing to provide a suitable "changing places" lavatory.
Adam George, 11, claims Flambards Theme Park, in Cornwall, discriminated and failed to make reasonable adjustments for him under the Equality Act.
Changing places toilets are required by an estimated 250,000 people in the UK who need extra specialist equipment.
Flambards says it takes inclusion of all visitors seriously and has made adjustments to its toilets.
The company says a permanent changing places toilet would cost over £40,000 - an expense that could affect jobs.
Adam, from Redruth in Cornwall, was born with a genetic condition that weakens his muscles, affects his speech and makes him a full-time wheelchair user. He also has autism.
But none of this has held him back and he loves outdoor activities.
His favourite place for a day out is the nearby Flambards Theme Park in Helston.
His mother, Rachel, says: "He loves rides. He loves things that go up and down and move him suddenly.
"He can't climb, he can't walk, he can't jump, he can't run, so all of the physical sensations that are well known to be vital to a child's developments are out of Adam's bounds, so a theme park enables him to have so many of those vital experiences."
In order to use the toilet Adam has to be hoisted on to a table, then on to the loo. He then needs to be hoisted back on to a large changing table.
Rachel is a member of the group Changing Places, which aims to increase access for those who need the extra space, hoists and changing tables provided in these toilet facilities.
In the past 11 years, the group has successfully seen more than 1,000 of the toilets installed across the country.
Flambards, though, doesn't have a toilet with changing facilities suitable for Adam's needs, so when the family visit, they need to hire a Mobiloo.
This is a large converted horse-box with the space and equipment Adam requires, but it can cost up to £350.
Under the Equality Act 2010, all service providers are under a duty to make "reasonable adjustments" to ensure that, as far as possible, disabled people enjoy the same experience as the non-disabled.
Rachel recognises that it is not reasonable to expect small cafes and shops to provide changing places toilets.
But she says: "A place like Flambards, a theme park, where they expect people to arrive in the morning, stay all day, eat, drink, stay late for the fireworks show, I personally think it reasonable that I can use the toilet when I go there.
"So why shouldn't Adam? Why shouldn't all disabled people be able to have their toileting needs met with dignity and safety?"
Adam's case claims that Flambards has discriminated against him and failed to make "reasonable adjustments" for his needs.
It is believed to be the first case brought on whether the provision of a changing places toilet is "reasonable".
It raises the question of what is "reasonable" in terms of cost for a business to incur in order to comply with the Equality Act.
What is a 'reasonable adjustment'?
Richard Smith, general manager at Flambards, says there are limits.
"Inclusivity is important to us to make sure that everyone has access to our park and the rides," says Mr Smith.
"However, there is an overall cost to put in a full-on changing places unit, and we've been quoted in excess of £40,000. That would have an effect on jobs possibly."
As an interim measure, Flambards has installed a mobile hoist and a changing bed in an existing disabled toilet.
"We're getting feedback from the disabled community on what's working and what's not, so we can carry on developing the structures we have in place," Mr Smith adds.
But Mrs George says the size of the toilet at Flambards and the equipment do not meet Adam's needs, and that she was not consulted when the park put in the new equipment.
She also disputes the £40,000 cost of a changing places loo, claiming one could be put in for closer to £10,000.
The Georges' solicitor, Chris Fry, of Fry Law, sees their legal challenge as part of a shift in society's understanding of disability.
"This case is part of an evolution in awareness of disability rights and how to enforce them," says Mr Fry.
"Adam's growing up in a more inclusive culture where disabled people quite rightly expect more for their money - if a venue advertises itself as accessible then it really should be fully accessible.
"This is a more inclusive world than it was, where a business can afford to provide the same service to everyone, society should expect them to do it."
Robert Meadowcroft, chief executive of charity Muscular Dystrophy UK, said: "Access to toilets is something that a lot of people take for granted, and it is shocking that families need to bring cases like this forward just to safeguard their children's dignity.
"We need to see building regulations changed so that all new buildings over a certain size - including theme parks - include changing places facilities."
Adam just wants to spend days out with his friends, but whether he can depends in part on what the law decides is "reasonable" for others to provide in enabling him to go to the toilet.