The full article in The Sunday Times.

The Times link is paywalled. This is the article, in the Daily Mail.

Basically they give no reason why this happened. And no reason why it should be seemingly restricted to cabin crew and not passengers. The whole incident does seem a bit odd.

British Airways crew left 'vomiting and dizzy' after 'toxic fumes' leaked into cabin | Daily Mail Online

Carbon monoxide and/or hypoxia for example can cause confusion and other described symptoms:
https://www.cigna.com/healthwellness...lertness-confu
https://cfpub2.epa.gov/ncea/risk/rec...TOKEN=19447862

The health effects associated with exposure to CO range from the more subtle cardiovascular and neuro-behavioral effects at low concentrations

After landing some passengers spoke about CO:
“It was pretty scary,” he said, adding they were told there were some technical problems with the plane. “The cabin crew on the top deck weren’t feeling very good because it was something to do with some carbon monoxide or something, that’s what [the firefighters] were talking about,” he said.
British Airways flight forced to land in Vancouver after crew members fall ill | Globalnews.ca

Hmm CO build-up next to outlets? doubt it, I was thinking more of an introduced agent.

It's not paywalled - like I said, you just have to register.

Flight crew ?spaced out? on fumes | News | The Times & The Sunday Times

The cabin crew all happily deplaned and walked into the hospital so it is unlikely that Carbon Monoxide was to blame as recovery from that takes some time as the haemoglobin has been bound with the carbon monoxide into carboxyheamoglobin which will take nearly an hour of 100% oxygen or ~6 hours with normal air to recover from.

Even Carbon Dioxide at high concentrations can give similar symptoms to those noted at high concentrations known as hypercapnia - perhaps a leaking CO2 bottle?

Symptoms and signs of early hypercapnia include flushed skin, full pulse, tachypnea, dyspnea, extrasystoles, muscle twitches, hand flaps, reduced neural activity, and possibly a raised blood pressure. According to other sources, symptoms of mild hypercapnia might include headache, confusion and lethargy. Hypercapnia can induce increased cardiac output, an elevation in arterial blood pressure, and a propensity toward arrhythmias.[4][5] In severe hypercapnia (generally PaCO2 greater than 10 kPa or 75 mmHg), symptomatology progresses to disorientation, panic, hyperventilation, convulsions, unconsciousness, and eventually death.
https://en.wikipedia.org/wiki/Hypercapnia

The curious symptoms to me are "stuffing food into their mouths" and a metallic taste. The first almost sounds hallucinogenic - the second can be caused by lots of things. In the early 60's our high school metal shop had a closed and well ventilated area for spraying zinc chromate primer on our projects and we were told never to heat painted surfaces (typically zinc chromate). Acute metal fume fever perhaps? Can be caused by fumes from heated metal or metal dust (magnesium for example) or heated zinc chromate.

Wonder if any toxicology studies have been performed on Airbus new Scalmalloy that makes up the bionic partition between pax and galley as well as the jumpseat (at least on the 320)? Lots of new generation alloys being used in today's environment.

Won't be Foundryman's ague , unless they were up to a bit of brass smelting in
a spare oven, vaporized zinc is the cause , and the symptoms are similar to a bad Flu, or Malaria.

I suppose a new alloy could emit fumes, but modern metallurgy is so precise I cannot imagine such a novel characteristic escaping notice.

Simple case of mass hysteria.
Cabin crew talking to eachother about some imagined or minor symptoms, most probably one of them had eaten something wrong before the flight.
Not talking about it to the passengers so only the cabin crew affected.

I agree with the mass hysteria suspicion The fact that no passengers were involved when there were 400 of them on board the 380 and yet none reported any symptoms is simply not a sustainable alibi for the cabin crew's explanation of an on-board toxic fume event.

Along with the prior food ingestion explanation for the origin of the hysteria, there may also have been the possibility that some pollutant in the air in the crew bus that took the crew to San Francisco airport from their hotel may have been a cause of some of the cabin crew's subsequent symptoms. Or maybe something from the hotel itself affected them? The early days of the exploration of the causes of Legionnaire's Disease have a similar Sherlock Holmes-type series of conjectures as to the origins of the ailment.

3 crew and 1 pax - Canadian TSB
 

Although 25 crew and 1 pax were taken to hospitals for observation, TSB reports 3 crew and the one pax were "affected by the fumes". Hardly mass hysteria and doesn't seem to track with latest release of info which implied zombie crew, crew lying on the deck, etc.

Without prejudging the cause, one possible source of contamination is organophosphates from engine oil; wanting out of that environment is hardly "hysteria"

Its the same on most big jets. I had an incident on a B767. There was a smell incident in the rear galley. One of the four cabin crew working there was incapacitated by the smell, and was taken off the aircraft by the paramedics and stayed in hospital overnight. The other three crew in that galley were not really concerned. I went to investigate, and finally found that the toilet/galley vent exhaust fan in the back of the bulk cargo hold had burnt out and tripped its CB. So I removed the plug and the aircraft departed (there are two fans). The steward that went to hospital was really bad, and he smelt the fumes from this burnt out motor in the galley about 1.5 meters above the fan.
The other 3 crew standing beside him were OK.
We wonder at times what they are thinking.

I was once in a group in a lab that suffered from CO poisoning , v similar symptoms........

They should check BA's customer service centre for the same smoke.