It has always been, quite rightly in my view, relaxed around Old Warden in respect of checking of who has bought a ticket and who hasn’t.
it was very easy to walk through the shop and onward to the displays with only a sticker on your jumper to indicate that you had paid.
I suspect a few of the cafe visitors may have been gaining free access to the museum and OW had to take more positive control of it - there is always a minority that will spoil it for the majority.
As someone stated earlier, buy an annual membership and gain unlimited access for 12 months - they have had next to no income for 12 months+.