Always tip cash

The bastards:

Employees of Tragus - which owns Café Rouge, Bella Italia and Strada - have come under pressure to ensure service charges are paid by card, and at least one waitress has told the Observer that they are being threatened with dismissal if they do not generate enough card tips. ...
Cash tips go directly to staff, but those paid by card go to the company. ...
...Tragus had sent a memo to restaurant managers telling them to crack down on employees encouraging customers to leave cash. Staff are forbidden to tell customers that the optional service charge is used to subsidise the national minimum wage paid to waiters.
...
A waitress in one Café Rouge restaurant claimed that the manager produced a weekly league table showing how much each waiter had collected in service charges. Those in the bottom three were denied the free food enjoyed by their colleagues. If this happened two weeks running, they could be sacked. Tragus denies this.
...
“I love my job, but the bottom line is this: if you want to help Tragus pay my wages (around 14% of it), then leave a tip on your credit card. However, if you want to tip me for the service you have received, I'd be very grateful for a couple of quid in the tip tray.”