Payment that isn't taxed or NI'd.
That it's been found to be a discriminatory practice.
It creates an unstable and potentially unsustainable market for labour in the restaurant business.
Countries where tipping is higher have higher rates of corruption.
that it allows restaurant owners to pay shit wages? yeah, so what's new? sadly your principles don't pay your waiter's rent.
always ask who gets the tip if you add it on your card.
leave cash if you have it, you'll be remembered and the next time you come back, you'll be treated like a king / queen.