Comment by toyg
No, it's designed to maximize what they can raise without pissing off too many voters. Even as it is, it's going to raise barely half a billion pounds, which is relatively insignificant in a budget worth hundreds of billions; but it's something, and something they (think they) can sell to their core electorate as a bit of token redistribution, when in reality it's just a cash-raising exercise.
If they'd targeted the really rich harder, it would have looked more consistent but would have probably raised even less (because, when a tax starts being significant, the really rich have the means to find ways to avoid it). As it is, it looks insignificant enough that the really wealthy will just pay it and move on.
> because, when a tax starts being significant, the really rich have the means to find ways to avoid it
Taxes on property are something they cannot avoid though.
One of the reasons the rich are able to find means to avoid taxes has always been government reluctance to stop them. There are many deliberate tax breaks for the rich - think of how long it took to get rid of non-dom status, so I really do not think the government has ever tried very hard to stop avoidance by the rich.