▁hyd ra ul ically , ▁they ▁form ▁a ▁single ▁fen . ▁In ▁total , ▁the ▁f ens ▁occup y ▁an ▁area ▁of ▁around ▁. ▁ ▁Most ▁of ▁the ▁f ens ▁were ▁extra - par och ial , ▁consisting ▁of ▁a ▁huge ▁common , ▁on ▁which ▁people ▁from ▁the ▁surrounding ▁villages ▁had ▁gra zing ▁rights . ▁These ▁could ▁only ▁be ▁exerc ised ▁in ▁summer , ▁as ▁prior ▁to ▁d rain age ▁works ▁being ▁carried ▁out , ▁the ▁East ▁Fen ▁dra ined ▁north wards ▁to ▁the ▁Ste eping ▁River , ▁and ▁during ▁the ▁winter ▁months , ▁most ▁of ▁that ▁river ▁dis charg ed ▁into ▁the ▁fen , ▁causing ▁w ides p read ▁flo oding . ▁ ▁History ▁The ▁area ▁has ▁been ▁subject ▁to ▁flo oding ▁for ▁centuries , ▁both ▁from ▁the ▁rivers ▁and ▁from ▁the ▁sea . ▁While ▁there ▁is ▁evidence ▁for ▁occupation ▁of ▁the ▁region ▁by ▁Rom ans , ▁Sax ons , ▁Dan es ▁and ▁Norm ans , ▁the ▁first ▁references ▁to ▁flo od ▁def ences ▁occur ▁in ▁the ▁ 1 1 th ▁and ▁ 1 2 th ▁centuries , ▁when ▁mon ks ▁built ▁a ▁sea ▁bank ▁to ▁hold ▁back ▁t ides ▁from ▁their ▁agricult ural ▁land . ▁A ▁sl u ice ▁was ▁constructed ▁in ▁ 1 1 4 2 ▁on ▁the ▁River ▁With am ▁to ▁improve ▁it ▁for ▁navigation , ▁and ▁Comm issions ▁of ▁S ew ers ▁were ▁appointed ▁in ▁the ▁ 1 3 th ▁century . ▁They ▁were ▁emp ower ed ▁to ▁investigate ▁any ▁problems ▁with ▁the ▁d rain age ▁of ▁the