This practice seems to be well established by now. Here is an article published in
2003 when it was emerging:
https://www.thecaterer.com/archive/h...-fierce-debate
A Savoy spokeswoman said the optional charge was an alternative to cutting back on the variety and quality of services expected at luxury, five-star hotels in a slowing economy.
She added that it rewarded back of house staff who are less likely to be tipped than other workers, helped offset the increased costs of living in London, and solved the guest dilemma of who and how much to tip.
The first part is rebutted by others who were interviewed for the article. The last part would only be accurate if the hotel mentions the charge at check-in -and- enforces a property-wide No Tipping policy which causes bell and waitstaff to decline cash tips.