During The Great War in 1914, Germany's blockade caused food shortages, which increased the demand for food production at home, with strong government influence over gardening. Private gardeners are encouraged to give seed stock to allotment holders.
One source or land suitable for allotments, but not large enough for general agricultural use is the land owned by railway companies.
These parcels of land are allotted to the railway workers and this is the reason that you will often still see allotments by railway lines today.
The RHS (Royal Horticultural Society) were involved in a government food production campaign, sending bulbs and seeds to POW's (Prisoner's of War) in German camps.