Twilight check-in question

We'll be flying from LGW in a few weeks time, and we're considering doing twilight check-in as we'll be staying the night before at the Hilton. What I was wondering was if we check-in the night before we fly, are we able to go into the departure lounge (and obviously come back out again ) during the evening, or are you only able to pass through security on the day you travel? I'm only wondering because we'll have time to kill on the Saturday night, and will be wanting to find somewhere to eat (probably Frankie & Bennys in the south terminal, though that is landside).

Anyone ever tried it, or know what the rules are? I'm not even sure we'd want to, but it would be nice to know if we could or not

I am 99% certain they will only let you through security on the day you travel. Otherwise, you could make use of the Duty Free shops while airside and then bring tax free goods back into "the country", i.e. landside, without departing.

Or, if you can go airside on the day before departure (some poeple must do twilight check-in then want to sleep in the lounge to try and save on hotel costs) they would only let you back landside in the event of an emergency / fire alarm etc.

Thats kind of what I thought would be the case. I've just never seen anything to say so