Acorn House, 69 Swinton Street, WC1 (020 7812 1842).
Prides itself on being London's first completely eco-friendly restaurant, so serves purified tap water and recycles 100 per cent of waste. The menu of sustainable fish includes Cornish mackerel, French sea bream and hand-dived scallops from Dorset.

Moshi Moshi, Broadgate, Liverpool Street and Canary Wharf (www. moshimoshi.co.uk).
A conveyor-belt sushi chain with all fish caught and delivered to the three branches within 24 hours. Excepting tiger prawns, all fish is sustainable, so salmon, mackerel, freshwater eel and crab can be knocked back, guilt-free, with one of their five sakes.

Arbutus, 63-64 Frith Street, W1 (020 7734 4545).
Awarded a Michelin star this year, Arbutus has helped push the Soho eating scene upmarket. The vast majority of their fish is eco-friendly, including Cornish pollack, grey mullet and Icelandic cod.

Konstam, 2 Acton Street, WC1 (020 7833 5040).
Trout, brill, herring and salmon are sourced from the Thames for their kitchen. Don't think murky London sluice, but clear Thames Estuary waters downstream.

Fishworks, nine branches in London (www.fishworks.co.uk).
Working with a small, selected bunch of fisherman, Fishworks says its sustainable fish sources are 100 per cent traceable. Whitebait, herring roe and haddock fishcakes can all be ordered with a clean conscience.

Wahaca, 66 Chandos Place, WC2 (020 7240 1883).
Run by Thomasina Miers, Wahaca specialises in Mexican street-style food. No booking policy so arrive early for fully-sustainable fish tacos or mackerel tortillas. A shot of their excellent tequila might not hurt either.