Huh? There will be zero impact for connecting passengers using Flight Connections, since international arriving pax using Flight Connections do not ‘land’ themselves, i.e. go through this UK immigration - they land and depart remaining airside.
It is a different story if the passenger decides to include a stopover, of course, but that isn’t what the OP asked.
Already said this but you weren't to know as my previous replies have been deleted. Why on earth they were is known only to the mods. I'm getting sick of not being informed as to why perfectly decent posts are being removed.. As my replies contained nothing 'deletable' under a/net rules, I therefore have to assume (no doubt unjustly) that VSMUT replied to the ongoing conversation with something untoward (blame the mods VSMUT).
For the record, the major UK airports don't require a transiting passenger to enter the UK. The passenger will remain sterile in the airside areas of the airport.
LHR and LGW especially so, just follow the purple 'Flight Connections' signs/lanes. Security will have to be re-cleared as this is a mandatory requirement, regardless point of origin,.
For VSMUT, who was insisting he has to enter the UK and go landside for a connecting international->international transit flight.
You only have to do this when transiting if you are doing something funky, eg. separate tickets for inbound and outbound connecting flights or on an airline that does not interline/through check baggage, eg Norwegian.
If neither of these apply follow the purple flight connections signs/arrows/lanes. If you're not sure what you're supposed to be doing, follow them too. It's what they are there for, you'll get quickly filtered through the right channels (with a spot of queue jumping if the connection is tight).
LGW https://www.gatwickairport.com/at-the-a ... nnections/