Most London restaurants add a discretionary service charge, usually 12.5%, sometimes 15%. If you see this line, it is your tip — no need to add more. It's legally optional, so you can ask for it to be removed if service was genuinely poor, though most people pay it without questioning it.
If no service charge appears on the bill, 10-15% for a sit-down meal is standard. Card machines often prompt you to add a tip before you enter your PIN — you can decline this if a service charge is already on the receipt. Pubs and bars are the exception: tipping at the bar isn't expected at all.
Watch for bills labelled “admin charge”, “brand charge” or “ambience fee” instead of “service charge” — recent UK law requires tips to be passed to staff in full, but charges under a different name aren't covered by that rule. If you want your money to reach your server directly, leaving cash is the more reliable option. For black cabs and licensed minicabs, rounding up the fare to the nearest pound is normal; a bigger tip for help with luggage is a nice extra, not an expectation.
More on how automatic service charges work in general →
Open the calculator with 12% pre-set →