The "world's first" crisp sandwich shop has sold out within two hours of opening.

Simply Crispy in Belfast enjoyed overwhelming demand for Tayto cheese and onion flavour inside the white floury Belfast bap.

The pop-up cafe offering 35 different flavours opened following a spoof suggestion by the Ulster Fry satirical website and came after the establishment of a breakfast cereal outlet in London.

Lines of mainly teenagers and 20-somethings formed from around 11am on Monday morning. By shortly after 1pm the snack bar had run out.

Crowds snaked their way through the tiny premises in Belfast city centre, dominated by a head-high stack of crisp boxes and bottles of sauce lining the wall. The atmosphere was jovial, with many people taking selfies.

To make the sandwiches, a precarious-looking pile of crisps is quickly compressed with a crunch by two weighty slabs of thickly-buttered white bread known as a Belfast bap, which is approaching burned and relatively tough on the top, but fluffy on the inside.

Customer Nerys Coleman, 32, from Belfast said: "It is something from your childhood. I have not had a crisp sandwich since university and before that childhood so it is bringing back the nostalgia."

Despite one curious passer-by putting her head through the door and asking: "Are you for real?", o wner Andrew McMenamin, 35, from west Belfast, said it was a serious business venture.

"I have been told it is the world's first," he said.

He said a Belfast bap and Tayto cheese and onion were the most popular choices.

"It is a school thing, people remember it from their school days, it is a classic and it is old-school."

Mr McMenamin, who owns That Wee Cafe, offered to transform his business when he read the spoof online. It is expected to run for three or four weeks.

Customers were able to choose their bread, crisps and add cheese or ham to their sandwich, served with tomato soup and chips.

On the menu at 8 Bedford Street are intriguing combinations that include traditional flavours such as prawn cocktail and spring onion, alongside Monster Munch and Frazzles.

Ms Coleman, who works for a firm specialising in foreign direct investment data, said she would not call every day but added lunch cost her around £3.

"We just decided to come round to lunch for the novelty - but we really like crisps as well."

She had smoky bacon flavour in a Belfast bap with chips.

"It is lovely, I think it is good and I would probably come back if I had a notion for a sandwich."

She said she liked the convenience - despite the obvious health issues.

Tayto, a Northern Ireland-based crisp manufacturer which is one of the largest distributors in the UK, provides most of the crisps "due to its large variety", but Walkers is also represented.

Mr McMenamin added: "We are riding on the back of the publicity the cereal cafe got in London, if it helps us and Ulster Fry then it is a good thing."

The idea has been credited to comedy writer Seamus O'Shea and his writing partner Billy McWilliams, who run the Ulster Fry website.

The Cereal Killer Cafe opened in Brick Lane, London, last year and sells classics like Rice Krispies. It was established by Belfast twins Alan and Gary Keery.

Mr McMenamin would not be drawn on the long term prospects for his own novel venture.

"It is certainly play it by ear, hopefully it will rekindle childhood memories of Belfast baps," he said.