Video report by Rupert Evelyn.
Food prices are likely to rise after farmers in England and Wales reported poor harvests due to the rainy summer.
Wheat yields fell 14.1% this year on a five-year average to levels last seen in the late 1980s, according to a survey by the National Farmers' Union (NFU).
The figures have been released after the wettest summer in England and Wales for 100 years, with 14.25in (362mm) of rain falling in June, July and August.
The British Retail Consortium (BRC) has already warned of price "pressures" following the worst drought in 50 years in the US and a heatwave in Russia.
Guy Gagen, NFU chief combinable crops adviser, said wheat yields were down after abnormally high rainfall across the UK since the early summer.
"The poor UK harvest compounds a series of challenging weather events for farmers around the world, most notably drought in North America," he said.
"The resulting tight supplies of many feed grains have driven up the prices of agricultural commodities around the world.
"These UK harvest results will do little to alleviate the global dynamics of commodity prices, with the prospect of relatively high commodity levels through to 2013.
"Cereals prices impact directly on other sectors, especially pig and poultry farmers who are already struggling with higher feed costs."
Richard Dodd, of the BRC, said: "There certainly are price pressures in the system which are coming from poor wheat harvests in this country but also in the other big wheat producing countries.
"The most recent figures are that wheat prices are up something like 29% compared with a year ago.
"Our own figures for the shop price inflation for food show that it has been very, very stable - it has been 3.1% for the last three months which is actually a two-year low. There is no food price explosion going on but there are pressures in the system that will work through.
"Our fiercely competitive retail market is protecting customers from the worst effects of these price pressures."