Name: Oliver O'Brien

From: London

How long have you been collecting? Since London 2012

How many pins do you own? 20

I started my Games Maker shifts at London 2012 with only a passing awareness of pin trading. But I was working in the Media Centre, and it was hard to escape the ever increasingly gleaming lanyards of the squaddies, G4S guards and media, the latter in particular who came to London armed with sets of pins. I still wasn't going to take part, until I got my first of the four Games Maker pins - and a colleague donated an Apple "Union Flag" pin. That was all it took to get hooked.

Lunchtime breaks in the Olympic Park involved travelling to the main pin trading areas and a couple of obliging sponsor pin hand-outs - all thoughts of eating lunch forgotten. I developed a quirky strategy, focusing on pins relating to where I worked and who I worked with - which meant more dedicated collectors acquired the sought-after NOC pins from me on the cheap!

Some people took it way too seriously - such as the guy hoarding multiple BBC Gold pins which were very rare. Apparently, only the Chinese CCTV pins were worth more to him, as he was thinking of pins in financial terms. Not really the spirit.

Anyway my favourite story was on my last day in the Park. It was a busy final afternoon, with the media rushing from the Media Centre to the Olympic Stadium for the Closing Ceremony. No time for me to watch TV, it was all hands on deck. But finally my team leader came over, and to my surprise let me go early, so I could run across the Park, grab a train, and watch most the ceremony at home. One problem - the thousands of athletes streaming in a giant line across the Park, into the stadium, were a physical obstacle between me and the railway station.

Eventually I managed to squeeze between two groups of nations, but not before one particularly joyous nation had been particularly happy to smile at me, give me a wave and pose for my camera. They were only too happy to give me what is my most treasured badge of all - the Uganda NOC. I wasn't sure why they were so happy. It was only when I got home, and caught up with the day's events, that I realised that Uganda had just won its first gold medal of the Games, on the very final event - the men's marathon. What a great way for them - and for me - to finish an amazing two weeks.