ww1 British large pack

[kradman]

Picked this up but the strap system on the rear is a bit odd has any one seen this system before , thinking its ww1 but not sure

[ILH]

I haven't seen this exact set up before but i'm pretty certain it isn't Pattern. The use of a twigg buckle and a pack buckle, along with the lack of brass tabs on the strap ends suggests a field modification or an army surplus mod (alot of stuff was cobbled together for civilian use post ww2). The lack of buckles and loops for the pack support straps would incline me towards the surplus side.
Sorry I can't be conclusive, Jim.