I came across a pair of stainless steel posts as I was walking on the Thames Path near Kew. They mark the original meridian line that passed through The King's Observatory which was founded by King George III in 1769. The Observatory is visible in the gap between the posts - it is now a residence. Walking past Syon Park, Isleworth, over Kew Bridge and onto Brentford, the River Brent and Boston Manor Park. I ended the walk off Northfields Avenue 3 hours later.