That is twice the size of the market for fish and chips, and reflects increasing sophistication among Britain's snackers. Bacon and avocado, pastrami and salted beef, and chicken tandoori have moved from the margin to the mainstream. Nineties nibblers expect more than a straight choice of cheese and tomato, ham salad or egg mayonnaise when they go out to buy a sandwich.
Marks & Spencer, widely acknowledged as spearheading the sandwich revival, is the largest retailer in the field. It started making up sandwiches in staff catering units, and began selling those made up in-store in 1980.
Since then, the business has grown rapidly. Last year, the M&S Moorgate foodstore in the City sold 3 million sandwiches, outstripping the 2.5 million sales at the chain's Oxford Street store. All M&S sandwiches - there are now 75 varieties on the menu - are made up in four bulk supplying units. Many are exotic, but sales of old trusties such as cheese and pickle and ham salad still eclipse the new wave incomers.
Boots, which entered the market eight years ago, comes second in the sandwich sales league. It has introduced a gourmet range (duck and orange for instance) and is keen to promote 'healthy' snacking as well as satisfying the more sophisticated palate.
In third place comes Intercity OnBoard Services - which shifts 6.5 million sandwiches and has shaken off its long-held image as a purveyor of furled, unimaginative sandwiches. The new breed of Intercity sandwich is made up in Wigan, and transported by road overnight in refrigerated containers.
These are the giants of the sandwich business - but there is still ample space for the smaller players, according to Jim Winship, director of the British Sandwich Association, set up two years ago and aimed at boosting quality and hygiene.
Mr Winship believes the once-fragmented sandwich market has polarised as it has matured. Big chains are concentrating supply on fewer manufacturers, equipped to deliver rapidly. This has put pressure on other sandwich makers, some of whom have gone to the wall.
But the economic downturn has also brought good news for the sector, according to Mr Winship.
'It is a market which has thrived in recession, as companies cut back on expense account lunches. Both chains and sandwich bars are catering for increasingly sophisticated tastes.'
In the hard-hit City, the arrival of M&S has had a huge impact. Old Etonian Robin Birley runs an unashamedly upmarket sandwich shop just a few yards from M&S - one of five outlets he owns in the City. Boardroom deliveries are a regular feature of Birley's business.
He is reacting by bringing in ready-made, off-the-peg sandwiches to complement the bespoke butties Birley's is known for. 'I think the market has changed,' he says. 'People have become more price conscious and there is a demand for quick service.'
While the big-hitting chains and established sandwich bars seem to be weathering the recession, the future looks far from rosy for the industry's minnows.
The Food Safety Act imposes stringent requirements on those handling and selling food. It must be kept at temperatures under 5C. Long-term career prospects for a man on a bike with a basket full of home-made sandwiches and no access to refrigerated storage look bleak.Reuse content