Tax evasion is not legal.
Tax planning is legal, and is ordering your financial affairs so that you pay the minimum tax legal. This is sometimes called tax avoidance.
Because of the behaviour of a number of companies and rich people tax avoidance has now come to be associated with the grey area around doing bizarre financial tricks, tricks which will be changed as the law catches up, to reduce tax obligations beyond a point that most people would call reasonable.
Very few people are asking for Google to pay full taxes. But if you have staff here, and you sell services here to people here, then you should probably pay some tax on those earnings here.
Google might be able to ride out the storm - there's not very many Google stores for vandals to deface. And they're lucky that they employ all those smart people. Any laws the UK gov makes will be fairly easy for Google to hop around.
(I day dream of Google AI / GA programming competitions where the algorithms battling for survival are those that robustly reduce tax burden to a fraction of a percent.)
