"5 poles or thereabouts" is the size of the allotment as stated on the contract with the local council. The pole is a unit of measurement dating back to Anglo-Saxon times- about 5 1/2 yards. I've paced it out and the allotment is indeed 5 poles by 5 poles (or thereabouts).
 The concept of an "allotment" probably goes back centuries -perhaps this is why an archaic measure is used- but the ones we have today are a legacy of the 19th. century. Land was made available for the poor to feed themselves, particularly in the expanding towns and cites as industrialisation replaced a more rural society.
 10 poles was reckoned sufficient for a family. Maybe this allotment was split in half at some point; most on the site are 5 poles but several are 10. The neighbours on the allotment beyond grow a fantastic array of dye plants (as described on their website Nature's Rainbow).
 On a soggy grey day in December the beds are fallow but it's a good time to ponder the year ahead. More herbs in the largest bed? Broad beans or borlotti beans? Persist with the rhubarb or try something else?
 Over the next few days I'll re-define some of the beds, make them a bit larger and cart some muck to improve the soil- leaf mould, kitchen compost and dung. My father purchased sackfuls of alpaca poo from a lady on a market stall who keeps a herd of them. Send the reindeer where they're needed Santa we've got alpaca.