E European airlines at Heathrow at weekends
Let's get away from all this security stuff for a moment.
A number of carriers, particularly from Eastern Europe, are developing a trend to serve London through Gatwick, but operating a token rotation through Heathrow, generally on Saturdays when there are one or two slots available.
Now perceived wisdom is you don't want to split operations, particularly low-volume operations, like this, so there must be a reason behind it. Pulkovo (now Rossiya) has done it for a while, now Air Ukraine and Azerbaijan Airlines are doing the same.
Is there some advantage should a couple of free slots come up in having an existing presence at the airport ? It can't be because of Heathrow's business traffic advantage as the slots used are on a Saturday.