Thanks for all the comments. I should point out that I never said that I was planning to do this, but I do have the old-fashioned view that a tip should be given for good service and the amount should be decided by the giver. Yes, the culture is different in the UK and elsewhere in Europe as someone points out.
Once the discretion is removed from tipping, the payment becomes a (another) service charge, which is a shame because the incentive to provide exceptional service is then lost - unless of course yet another layer of additional tips is given. (a third layer by my reckoning).