Originally Posted by
Swanhunter
The 10% surcharge is sufficiently rude that I won't tip. No credit card company charges anything like that as a fee so it is purely to fund Dialacab (and partly offset the driver having to pay tax on that bit of income too

).
Not sure I'd consider 10-15% a normal black cab tip. I normally round up to the nearest pound (or the nearest plus one over £15) and am normally thanked genuinely for it.
Had one on Sunday who automatically rounded up to the nearest pound and where I was expecting £5.40 back from a £20 (before tip) only got a fiver. He took a really slow route when I was expecting to go the usual route via Lancaster Gate and get there far quicker. Going through Hyde Park is not what I call quick and I told him so, we took 20+ minutes to do what is normally a 15 minute journey in other cabs going the other route. He then drove off before I could say anything so I assumed he'd tipped himself as I think he'd worked out I certainly wasn't going to bother.