Brother's appearance

In the 1980's I was living in Lewisham in South East London, and wanted to buy a typewriter. I scanned Loot, the listings magazine that covered the whole of London, and found one for sale in Twickenham, in West London. I went there (to a house, not a shop) and bought the typewriter. As I was leaving I glanced at a pile of letters on the desk, and saw that the top one had been written by my brother. It was a business letter, and addressed to one person, not a circular. At the time he was working for a housing association, so would have been writing letters regularly. However, the area he covered was Pimlico, which is a long way from Twickenham. My rough estimation of the odds of this is: - assume he was writing 10 such letters a day - about 3500 per year - assume there are 3,500,000 households in London, as covered by the listings magazine - so if the letters were sent randomly the odds per household would be 1000 to 1 - however, most letters would be sent to Pimlico, so estimate 10,000 to 1 for other areas - even if received by the household, the odds that the letter would be visible and I would notice it must be 100 to one - so this gives final odds of 1,000,000 to 1 I'm not sure how significant this is when assessed over a lifetime, but it still seems fairly remarkable. Paul