One of the biggest problems is that the CLoCK study is going to say 'oh, these symptoms are very common. Look, the children who weren't infected with Covid (as evidenced by a negative test) have just the same sort of symptoms. So, Long Covid isn't a thing.'
So, again, there's trouble with a vague WHO definition of Long Covid, this time a paediatric one. I think Long Covid as a term needs to be abandoned now. Instead, refer to post-Covid ME/CFS (requiring PEM) and post-Covid fatigue syndromes (not requiring PEM).
And trouble with assuming that a negative Covid test equates to not having had Covid.
I guess we can't stop the CLoCK study, but perhaps, like the fairy godmother in Sleeping Beauty, we can limit the damage. We could demand some additions to the protocol that make it less harmful. e.g.
* require periodic testing of the young people in the Covid negative group for Covid antibodies (not the ones given in vaccinations)? If they test positive to the antibodies, remove them from the Covid negative group.
* if people in the Covid negative group report having Long Covid symptoms (eg debilitating fatigue), take a family history of Covid infections around the time of the Long Covid onset in the young person. If close family members did have a Covid infection around the time of onset, then it can be assumed that the young person did in fact have a Covid infection, but, for some reason tests haven't found the antibodies, and so they should be removed from the Covid negative group.
* require the assessment of all young people in the study to be assessed for PEM, and for ME/CFS using a criteria that requires PEM (e.g. the NICE one, or the IOM/NAM one)
Regarding the UCL reply that it is standard practice when assessing the mental health of young people to use a questionnaire that asks about things like stealing, I think it is right to push back about this. Just because it's a standard questionnaire and has been used in assessing mental well-being in cancer, that doesn't make it right. It just compounds the harm. I can recall filling out a questionnaire for my 13 year old son, for an ME/CFS study, on whether he smoked or chewed tobacco, and if he was afraid of spiders. Enough with these stupid surveys. If it's a standard questionnaire, then update it, amend it, chuck it out and create a new one.
I think we could ask that the data from the questions of very limited relevance to Long Covid are deleted and not analysed. At the very least, we could ask that parents and the young people in the study are asked whether they would like to withdraw their data on these questions.
Edit - I note that the letter writers are calling for any reference to lockdown to be removed from the study. That seems like a good idea.