I went to visit an old school friend who had recently moved into a flat in a house in Muswell Hill, London. I rang his flat bell, and he buzzed me in to enter the hallway. To my surprise in the hall I saw another old friend - a fellow musician I had played with several years previously and had not seen for several years.
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<p>It turned out that he was coincidentally visiting the person who lived in the flat next door to the friend I was visiting!
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<p>The two people who lived in the flats had no other connection other than being neighbours. I did not know my musician friend's friend, and my school friend did not know my musician friend, so there was no possibility of the meeting being other than sheer chance.
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<p>It is still incredible to me that out of all the flats in London, two people who knew each other could meet, having independently planned to visit separate acquaintances, completely unbeknownst to each other, arriving at adjacent rooms at exactly the same time. (An additional coincidence - though admittedly not quite as staggering is that both of my friends were named Dave)