Revelations that Pizza Express is serving halal chicken meat has triggered a storm of debate about the ritual practice of animal slaughter and whether they really suffer more than those killed by other methods.
The Sun reported on its front page that all chicken meat in the chain's pizzas are killed in accordance with Islamic law and said this could cause animals "unnecessary suffering".
The Sun frontpage on Wednesday
The reaction was so great that both Pizza Express and halal began trending on Twitter.
For meat to be halal, an animal has to have its throat slit by hand while it is still alive. An accompanying editorial in The Sun conceded that there was actually "no unusual cruelty issue" if animals were stunned before being slaughtered, as is standard for non-religious slaughter.
It also emerged that Pizza Express had said on Twitter in 2012 that all its chicken was halal.
But people took to Twitter to point out it was a misconception that most animals that undergo halal slaughter in the UK are not pre-stunned. In 2011, the Food Standards Agency noted "a majority" of them were.
People debated why the paper was singling out Islamic practices for scrutiny. The Sun article followed a Daily Mail report last week that said 185 Subway stories - of the 1,500 there are across the country - were selling halal meat only.
Many people said killing animals using halal methods was no more cruel than other methods routinely used.
Former tabloid journalist and author Susie Boniface said 88% of animals killed using the halal method are pre-stunned.
According to the RSPCA, most poultry slaughtered by machine are stunned by having their heads inserted into electrified water and then moved on a conveyor belt to have their throat slitted by a mechanical neck cutter.
Some chickens are are killed using gas, which has "some welfare advantages" as it does not require them to be shackled, the charity said.
People also discussed whether pre-stunning animals meant they could not be halal, as some contend it is not.
The Halal Food Authority announced in February it would certify poultry being stunned using electrified water for halal purposes provided its representatives could oversee it and the stunner device operated above a certain frequency.
The RSPCA told The Daily Telegraph: “We recognise religious practices should be respected but we also believe animals should be slaughtered in the most humane way possible.”
Stephen Evans, of the National Secular Society, told The Sun: “Unsuspecting members of the public are routinely being duped into buying meat from religious slaughter methods.
“Meat should be properly labelled, enabling consumers to make an informed choice about the food they’re buying.”
The Huffington Post UK approached other restaurants and fast food chains asking whether they served halal meat.
In a statement, McDonald's UK said none of its meat was certified halal.
The statement said: "McDonald’s has a rigorous set of standards governing animal welfare practices and the quality, hygiene, safety and traceability of our food.
"These standards include the mandatory stunning of all animals prior to slaughter and do not include any references to halal requirements in the UK.”
Chicken restaurant Nando's said it served halal meat in a fraction of restaurants where it was clearly labelled as such but a "small proportion of chicken" sold in its other restaurants was halal but nor labelled as such.
A spokesperson said: "We have 314 restaurants, 64 of which serve only halal chicken and are signposted both in the restaurant and online.
"A small proportion of chicken sold in our other 250 restaurants is also halal and is not currently labelled when served. We continue to look at ways to offer chicken dishes which are guaranteed to be non-halal."
The spokesperson added: "All of our chicken suppliers meet the British Red Tractor Farm Assurance Standard and comply with all the European and UK animal welfare legislation. Chicken welfare is incredibly important to Nando’s and all of our Halal chickens are stunned before slaughter to minimise stress."