BEST friends are a bit like velcro sneakers; a brilliant thing that you totally took for granted as a kid, and they are really hard to come across in adult sizes.
When I was 10, I worked my way through about half a dozen best friends. They were made with pinky promises and lost by the unique and cruel discrimination of pre-teen girls.
As I grew up and through the formative years such of high school and university, I acquired a small but tight network of besties who I remain close to even though the physical distance between us is in some cases vast.
But as we all grew up and boyfriends turned into husbands, the traditional 'best friend' faded into lesser prominence.
We may not share things with our spouses in quite the same way we did with the best friends of our youth, but they are still our go-to guy and the person who is most likely to listen and help when needed.
The closest friendships I have had as an adult have been with females, and catch-ups have been of the "girly" kind - the men left at home because instead of being a friend, they are the boyfriend or husband of a friend.
That all changed when we met Steve and Amanda. New in town and from the South Island, they arrived three years ago and after initially overlooking each other at a barbecue cooking course, Steve and my man (who prefers to remain nameless) became mates along with a small group of other really cool guys who met every Thursday for a low-key after-work beer.
Eventually the men decided to introduce the women, and I went along to a dinner at a local winery, expecting the sort of forced conversations often had when spending time with the wives of your partner's mates.
What I got instead was three years of incredible friendship between four couples where all the women became as close to each other as all the men were.
It made for the best nights out, the best weekends away and (when we all had babies at roughly the same time) the best Sunday afternoon barbecues.
At the centre of all this were Steve and Amanda. Awesome hosts and always up for anything, they were the sort of best friends you didn't expect to encounter as an adult.
There was no putting up with Steve just because he was Amanda's husband, and my partner felt the same about Amanda. They were both just cool.
Then they moved away. It happened last week after Steve - a pilot - got transferred to Christchurch. When we were first told about the decision several months ago I felt like my heart was breaking. I never expected to find a friendship with a couple like them as an adult, and it seemed wildly unfair that they should now be leaving so soon after their discovery.
It has been many years since I broke up with a boyfriend I liked because he lived too far away, and I forgot how much it hurts to let someone you care about go because distance and work dictate it.
Of course we have plans to catch up soon, and there is the wedding between their daughter and our son to attend in due course, but it's not the same as having them around the corner and popping in for a wine without notice. Life without them seems a little bit empty - a sunny day that suddenly turns cold and cloudy.
Perhaps we will meet another couple of besties like them, but right now the emptiness feels complete.