▁and ▁John ▁Haw k sh aw , ▁based ▁on ▁an ▁earlier ▁design ▁by ▁Is amb ard ▁Kingdom ▁Brun el . ▁It ▁is ▁a ▁grade ▁I ▁listed ▁building ▁and ▁forms ▁part ▁of ▁the ▁B 3 1 2 9 ▁road . ▁ ▁The ▁idea ▁of ▁building ▁a ▁bridge ▁across ▁the ▁Av on ▁G orge ▁origin ated ▁in ▁ 1 7 5 3 . ▁Original ▁plans ▁were ▁for ▁a ▁stone ▁bridge ▁and ▁later ▁iterations ▁were ▁for ▁a ▁wr ought ▁iron ▁structure . ▁In ▁ 1 8 3 1 , ▁an ▁attempt ▁to ▁build ▁Brun el ' s ▁design ▁was ▁halt ed ▁by ▁the ▁Br istol ▁ri ots , ▁and ▁the ▁re vised ▁version ▁of ▁his ▁designs ▁was ▁built ▁after ▁his ▁death ▁and ▁completed ▁in ▁ 1 8 6 4 . ▁Although ▁similar ▁in ▁size , ▁the ▁bridge ▁to wers ▁are ▁not ▁identical ▁in ▁design , ▁the ▁Cl if ton ▁tower ▁having ▁side ▁cut - outs , ▁the ▁Le igh ▁tower ▁more ▁pointed ▁arch es ▁at op ▁a ▁ ▁red ▁sand stone - cl ad ▁ab ut ment . ▁Rol ler - mount ed ▁" s add les " ▁at ▁the ▁top ▁of ▁each ▁tower ▁allow ▁movement ▁of ▁the ▁three ▁independent ▁wr ought ▁iron ▁ch ains ▁on ▁each ▁side ▁when ▁loads ▁pass ▁over ▁the ▁bridge . ▁The ▁bridge ▁deck ▁is ▁susp ended ▁by ▁ 1 6 2 ▁vertical ▁wr ought - ir on ▁ro ds ▁in ▁ 8 1 ▁matching ▁pairs . ▁ ▁The ▁Cl if ton ▁Bridge ▁Company ▁initially ▁managed ▁the ▁bridge ▁under ▁lic ence ▁from