This is IMO and with respect a cop out..An 11 year old is not a kid..Even if a child was not trusted to hold a boarding card, then when the parents hand over the collective passes, there should be a headcount per pass..My daughter has always shown her own documents, and why are kids allowed to mingle before being properly processed?.
Well, yes an 11 year old is not really a small child, so without trying to blame anyone here, how come this alleged family didn't notice him tagging along? While yes lessons will have to be learned by staff, that aspect of this story actually concerns me just as much....
Aside from that, you obviously keep good control of your family heading through an airport, sadly some parents/guardians don't. I've seen children running ahead or darting about when they should be sticking close to the person holding the documents. Staff are under pressure at busy gate areas and don't have eyes in the back of their head to see a child slipping through.
The security in the U.K. is not infalable, but I tell you what it is a damn sight better than some places I have been.
Manchester actually goes above and beyond the requirements for passenger security screening, with the compulsory use of the (often considered controversial) backscatter X-ray machines if the metal detector picks up anything.
If Gatwick can have automated access gates to security where boarding passes are scanned and a photo taken, I cannot see why Manchester can't have them. It's not like Gatwick doesn't cater for infrequent travellers and large families.