On approach to Heathrow the First Officer (flying the aircraft) became incapacitated and was unconscious for at least a minute before regaining consciousness and able to get on to emergency oxygen (Eros).
Fortunately the Captain smelt the fumes, donned his oxygen mask and took control of the aircraft. We have full evidence and it has also been reported here:
http://avherald.com/h?article=4d189839&opt=0
(There are no sensors or monitoring equipment onboard bleed-air aircraft. The only sensors to alert crew of fume events are their noses.)
On Sunday 4th January the press office at British Airways made this statement:
‘It's not true that the First Officer passed out, he was feeling unwell but neither of the pilots in the cockpit say he fainted.
- Pilots regularly train to land by themselves so this is something the Captain would be prepared for.
- The unwell pilot was offered further medical support but said he didn't need it, and felt well enough to go home.
- There is an average of 151 engineering checks before aircraft fly again.
The Captain landed the aircraft safely, and customers disembarked as normal. As the First Officer was feeling unwell, he was seen by an airport paramedic as a precaution, before going home.’
The press office later confirmed that there had been a fume event and that a ‘Mayday’ had been called.
We know that the pilot was unwell and has been off work following the incident.
Is it just the press office saying that the pilot didn’t lose consciousness - or have both the pilots in the cockpit really NOT said or reported that the First Officer had lost consciousness?
We don’t know - but would like to.
We DO know that the aircraft was grounded on arrival. It went back into service on Tuesday 7th January 2020 as the BA478 to Barcelona at 07.50 GMT.

CAA Guidelines State:
See: Neurology - (7)
a single episode of disturbance of consciousness of uncertain cause - Class 1 AMC1 MED.B.065:
https://www.caa.co.uk/Aeromedical-Examiners/Medical-standards/Pilots-(EASA)/Conditions/Neurology/Neurology-guidance-material-GM/
Can this ‘episode’ be ‘satisfactorily explained’? Has the pilot in this case been assessed as fit to fly by his AME (Aero Medical Examiner)?
We don’t know the answer to that either, but it does raise a lot of questions:
1.  Has the pilot been examined at all?
2.  What if there is an underlying condition which contributed to the unconsciousness?
3. What if the pilot is extremely sensitive to the fumes from aircraft oil?
4. If he/she has been assessed as fit to fly, then has another episode of unconsciousness because of fumes from aircraft oil in his workplace (cockpit) will he/she then be assessed as unfit and then lose his/her license and possibly his/her career?
5. Has this actually been reported at all or has it been hidden/denied/brushed under the carpet by all concerned in order to keep the issue of contaminated air in aircraft under wraps?
6. More importantly, what if both pilots had become unconscious during that approach into Heathrow?
The financial costs to correct this bleed-air design flaw are going to be massive. Also, future litigation costs will be huge. So the reluctance to admit the problem from a financial perspective is understandable but from a health perspective - is immoral.
No doubt risk assessments have already taken place - of the risk of both pilots becoming incapacitated from fumes and the loss of an aircraft with all passengers & crew. They believe that risk is minimal - but they have come close on a few occasions - London Gatwick - Paphos on 19th October 2019 is another example, which this airline also deny was a serious safety issue:
http://avherald.com/h?article=4cfb5c82
British Airways are not alone in this issue. This is a Global problem affecting ALL airlines operating ‘bleed-air’ aircraft.
American Airlines:
https://www.paddleyourownkanoo.com/2020/01/04/american-airlines-reported-over-1600-smoke-odor-or-fume-events-last-year-and-thats-an-improvement/

You can view more here:
http://avherald.com/h?search_term=Fumes&opt=0&dosearch=1&search.x=0&search.y=0
Airline Union Advice:
https://www.ifalpa.org/media/3141/18hupbl03-cabin-fumes.pdf?platform=hootsuite

https://www.aerotoxicteam.com/balpa-may-2019.html

Airlines simply don’t care about people or the fumes from aircraft oil, hydraulic fluid, fuel and other aircrafts’ exhaust which they are forced to breathe in aircraft cockpits and cabins. Their only concern is for profitability.
The lack of action by the whole Aviation Industry and their complete lack of ‘duty of care’ have caused so many deaths and injuries to innocent people - which would fill thousands of aircraft worldwide - if not tens of thousands.
They have a choice. They can continue to deny there is a problem and keep spewing fumes into aircraft cabins & cockpits as well as lies in the media or they can do the right thing and come clean, which includes implementing solutions to end poisoning innocent passengers and crew onboard aircraft.
The alternative: To continue with this ‘charade’ could eventually become financially catastrophic.

For further information on this subject including medical advice, studies & testimonies, please visit: www.aerotoxicteam.com

On the Aerotoxic Team Website you can also purchase the ‘Flyers Friend’ protective mask (made by Cambridge Mask Co.) with a 10% reduction in price,  suitable for passengers onboard aircraft. Profits from the sale of the mask go toward the cost of running and maintaining the website which is done on a voluntary basis.

As an alternative to The Cambridge Mask there is Respro: https://respro.com/store/product/technotrade-plus