Corn, Malt, Flour & Hops.
includes Wheat, Oats, Barley and Rye grown in UK and Maize grown in USA.
In general England has always preferred to eat bread from Wheat while Scotland has preferred Oats. In the first half of the 18thC English corn production was in surplus. By 1760 demand began to outstrip supply. The population of England rose from 6.2 million in 1750 to 9.1million in 1801.
In 1689 an "Act for Encouraging the Exportation of Corn" came in, offering a bounty of 5s./quarter when the price dropped below 48s./quarter. A variable duty was to be levied on exports if the domestic price rose above a certain level. 
In 1791, with the coming war with the French, Parliament took on the power to prohibit the export of corn for a limited period of time. Traditional sources i.e. Europe and the Baltic were threatened by French harassment and blockade. This led to an expansion of UK wheat farming and high bread prices.
England was now heavily dependent on Irish corn surplus.
With the end of the war, the price of corn dropped by half. Parliament, made up largely of land-owners responded
by passing a law permitting the import of foreign wheat free of duty only when the domestic price reached 80s./qtr. During the passing of this legislation, Parliament had to be defended by armed troops against a large angry crowd. There was huge resentment by the people living in Britain's fast growing towns having to pay more for their bread while the farmers and land-owners grew fat on the profits.
The militant Anti-corn-law-league was led by Richard Cobden who became a member of parliament in 1841.
The economic depression of 1840-1842 increased membership of the league which by 1845 was the wealthiest and best organised political group in Britain.

The Corn Laws were eventually abolished in 1846 and the
duty on oats, barley and wheat reduced to the insignificant sum of 1s./qtr. This was a triumph of the new political power of the English middle class.

Flour is generally milled close to the point of consumption. It is easier to transport corn as grain.
The trade of malting is a large and extensive one, and is carried on in roomy buildings.  The barley is steeped in cold water for thirty or forty hours whereby it imbibes water, increases in bulk and emits carbonic acid.  After this steeping the water is drained off, and the wet barley is thrown in a layer about sixteen inches deep, called a couch, on the malt-floor where it remains about one day. It is turned over repeatedly, and the layer is gradually thinned or lessened in depth, during which a chemical process is going on, whereby the barley becomes heated, acquires an odour, exudes moisture and sends forth little sprouts or germs.  At a particular stage the maltster checks further germination by drying the barley in a kiln at a temperature between 90140 F.  By this change the barley becomes fitted to yield a sweet substance when in the hands of the brewer; and it now loses its former name to take up that of malt.  Three different kinds of malt are made and used in brewing; one pale or amber, for yielding the fermentable extract; one brown to impart a particular flavour; and one roasted or black, to give the dark colour which characterises London porter.

The hop is a plant of which the blossom only is used in brewing.  It requires rich soil, and its cultivation is attended with many hazards.  In April when the young plants have sprung up to a height of about three inches from the ground a number of hop poles are inserted in the ground.  These are of willow or ash from sixteen to twenty feet high.  The young plants are tied to them with withered rushes.  The harvest is in September.  The pickers carefully separate the blossoms from the leaves and stalks, and gather them in large sacks, which are carried home and laid in a kiln to be dried.  A merrymaking or hop-harvest-home follows in which a hop queen is chosen bedizened with ribbons and hop blossoms.  The dried hops are pressed very tightly into sacks.  The excitement among the hop-dealers both precedes and follows that of the hop-pickers. A speculator frequently buys a field of hops long before it can possibly be known whether the crop will be good or bad.  Hence it arises that the losses or gains are frequently enormous, scarcely any other commodity having caused the gain or loss of such large fortunes in a given time.

The Hop Queen