I've seen Thatcher blamed for pretty much everything that is wrong with the country today (and quite rightly so in my opinion) but I must admit this is the first time I have seen her connected to the demise of the red squirrels.
Anyway, I grew up on the edge of a small town in the south of Scotland, and have fond childhood memories of seeing the cute red squirrels playing in the pine trees outside my kitchen window, so it does sadden me a little to see grey squirrels in their place now.
One thing the article doesn't mention though is that part of the problem is habitat loss - the red squirrels particularly like to eat seeds from pine cones for example. And in my case most of the pine trees outside my old family home's kitchen windows were blown down in various storms over the years.
As an aside, I did have a problem in London a few years back with grey squirrels digging up my tulip bulbs. This is particularly surprising since I live on the fourth floor and just have a small balcony rather than a garden, so I don't quite know how they got there. But I saw them several times so I knew it was them. I felt like I was under attack and that they were taunting me. I was tempted to set up the solution described in "Militarizing Your Backyard with Python: Computer Vision and the Squirrel Hordes" [0] (although eventually went for the low tech solution of burying the bulbs below wire mesh).