About 2,000,000 quarters of wheat per annum supply the inhabitants of London with bread and flour. Poultry, being at times of high price, is attainable but by the more wealthy; but the meat market is well supplied, at a reasonable price. Large quantities of meat arrive in London ready slaughtered, not only in the steam vessels from Scotland and Ireland, but by railroads from the counties adjoining the Metropolis. This quantity is increasing, and may be estimated at one-eighth of the whole consumption. It may be worth while to remark, that, about the year 1700, the average weight of the oxen sold in the London market was 370 lbs. ; of calves, 50 lbs.; of sheep, 28 lbs.; and of lambs, 18 lbs.; the present average weight is-of oxen, 800 lbs.; of calves, 140 lbs.; of sheep, 80 lbs.; and of lambs, 40 lbs. 250,000 oxen, 2,000,000 sheep, 40,000 pigs 30,000 calves, 6,000,000 head of poultry and game, and 450,000,000 lbs. of fish, are brought into London annually for the supply of its inhabitants. 
    The hogs reared for the London markets are mostly kept by the malt distillers, who feed them on grains, and thus produce fine meat.
    The poultry, game, pigeons, rabbits, &c. consumed in the Metropolis are estimated to cost annually upwards of 455,000l.

Cruchley's London in 1865 : A Handbook for Strangers, 1865