Having to say goodbye hit home just how far away Mark and I really are, from everybody we're close to.
Like anything that allows you to escape the same-old, same-old drudgery of a weekly routine, three weeks of holidaying whizzed by much more quickly than anticipated.
Even though we're a few months yet from our one-year anniversary of Life in London, being able to show Mrs and Mrs Mark the parts of the city tourists would usually overlook kind of made me feel like London was home.
Standing in Terminal 3, we were given a sharp reminder that this isn't home, after all.
In some ways, waving goodbye at Heathrow felt worse than when Mark and I left New Zealand.
Back then, we had all of the excitement of our adventures ahead to keep us preoccupied: excitement at navigating our new lives in London, at seeing and experiencing the attractions Europe has in spades.
There was also a healthy dose of fear (would we be kidnapped in South America? Who knew?).
Back then, we were able to tell ourselves that not only did we have a lot to look forward to, we were also likely to be hosting visitors soon enough. Both of us were well aware how fortunate that made us, too.
But this time around, we knew that it would be a long time between drinks.
The chasm between the two of us and our families - not to mention our big mash-up of friends - was suddenly the elephant in the room.
Or, for accuracy's sake, the elephant on the Tube.
The ride home on the Piccadilly Line was quiet.
Although we have very different family dynamics, Mark and I each have cause for feeling sometimes like an 8-year-old who just wants school camp to be over.
I'm not sure who has felt our absence more keenly, them or us, but I do know that on our end, the fear of missing out and guilt for not being around for the big occasions do sting sometimes.
Mark and his sister are lucky enough to have one of the closest sibling relationships I've seen; not having Mum around, I spend many of my inward-looking moments wondering how what's left of my family is holding up.
Since we left Invercargill, we've missed birthdays, Christmas, weddings, and a graduation, not to mention the usual raucous Friday nights with our friends, which always seemed to involve cider and often ended up with the slater on the dancefloor at the Kiln or Tillys.
(Friends, an anecdote: our first trip to the Chatsworth lasted a mere two minutes, before Mark was airlifted out of the premises by two bouncers. He had cleared a circle in the middle of the crowd to make way for his killer moves, the most famous of which you will remember is The Swimmer. I guess London simply is not ready for his jelly.)
It would be easy to give in to homesickness. More people than I realised, before moving here, do.
But since our grand adventure began, Mark and I have trudged through the Amazon. We've swum in the Mediterranean. Paid our respects at Flanders Fields.
Imminent plans include our first white Christmas, in Austria (plus my first-ever attempt at skiing: I know, I'm ashamed of myself) and a trip to Iceland, where we will hopefully see the Northern Lights.
Away from all of our Life Squatters - the people who make your world that little bit easier - we've also been forced to become more self-reliant, more open to new experiences and saying yes.
Although there are times when homesickness threatens to take over, I think that, when we do make our way back, we'll be better people for it.
Till then, amigos.
- © Fairfax NZ News