Riverside herb

Riverside herb

Observation - Riverside herb - UK and Ireland. Description: This herb is carpeting many areas along a river stretch in our local park/woodland. It is predominantly at the banksides, and as of 14.5.14 not yet in flower. Looks reminiscent of Broad-leaved dock, and/or Common Bistort, but I don't think it's the latter

This herb is carpeting many areas along a river stretch in our local park/woodland. It is predominantly at the banksides, and as of 14.5.14 not yet in flower. Looks reminiscent of Broad-leaved dock, and/or Common Bistort, but I don't think it's the latter and certainly isn't the former. It has winged petioles at the leaf base and the stem reddens at its base. Leaf is very broad, around 8cm wide by 13cm long.
It's been bugging me for ages! Any help in Identification would be super!