Complex sentence: Livestock arrived either by boat or else on the hoof, usually from Smithfield Meat Market by way of London Bridge (though the slaughterhouses only operated in the cooler months of the year, October-April).
Split into simpler sentences: Livestock arrived either by boat or else on the hoof, usually from Smithfield Meat Market by way of London Bridge. The slaughterhouses only operated in the cooler months of the year (October-April).