Sandwich Sandwich’s Mark Lane flagship turns into an indoor picnic on Friday 7 August, with the first 500 customers through the door from midday getting a free Birria Beef Sandwich, made in partnership with Heinz.
Sandwich Sandwich built its reputation in Bristol over a decade before its first London site on Gresham Street pulled hour-long queues on opening day. Mark Lane, its second London outpost, is bigger again, 3,500 square feet and billed by its founder as the biggest sandwich shop in the UK. For one Friday, that flagship becomes something else entirely: an indoor picnic, built specifically so the queue has somewhere better to wait than the pavement.
The sandwich
Birria has spent the last couple of years as one of the biggest food trends on social media, all slow-braised Mexican beef and rich consommé for dipping. Sandwich Sandwich’s version packs pulled beef birria, Manchego, crispy onions, lime and queso crème fraîche, Heinz Chipotle Mayo, cucumber, rocket, coriander and diced white onion into fresh-baked bread, with the consommé served alongside for dipping. It’s the trend translated into the shop’s own house style, which has always meant filling first and everything else second. The Birria Beef Sandwich runs for one month across all Sandwich Sandwich sites in London and Bristol, not just for the launch day.
The indoor picnic
For the launch itself, Mark Lane gets artificial grass, trees, picnic blankets, live music and complimentary drinks, a full picnic setup indoors regardless of what the weather is doing outside. The first 500 people through the door from 12pm get their Birria Beef Sandwich free. After that, the picnic is just for the day, but the sandwich stays on the menu for a month.
The London x London Take: Free food events in London tend to mean a queue that isn’t worth the wait, but 500 sandwiches is a genuinely large giveaway and Sandwich Sandwich’s portions have never been shy. Turning up right at midday matters here far more than usual. If you miss the free 500, the sandwich itself is worth going back for within the month regardless.
Need to Know
- Where: Sandwich Sandwich, 70 Mark Lane, London EC3R 7NQ
- When: Friday 7 August 2026, from 12pm
- Free giveaway: First 500 customers only
- Sandwich availability: One month, across all London and Bristol locations
