Years ago my parents were very keen to buy at a house in Lebanon gardens. My father who is a civil engineer happened to go for an interview somewhere and saw the plans to turn the south circular into a 3 lane motorway (I think it was going to be the M15 (the M25 was the middle sized of 3 proposed concentric circular motorways around London!)
Anyway the motorway was pretty much going to be on top of the garden of this house. So they didn't buy it and instead bought the house I grew up in in Fulham. The missed house had a swimming pool in the garden! I only found this out when we bought our house a few streets away and my parents told us the story. I probably would have gone to different schools, never spoken French and been an Olympic swimmer, but I might have met my husband as a teenager as I would have been closer to where he grew up!
So engineering projects don't always happen
Also, my dad first started working on cross rail in the 1970s, so that took half a century to build!