Ressurecting rhubarb

clean any rubbish off and use a couple buckets well rotted compost / manure around it put straw loosely over the top of the crown about 6 inch deep

Now's the time to also consider whether the rhubarb is really in the place you want it, Mrs Veg. By moving the roots, you will revigorate the plant as well - in a better location. Once you dig up the roots, look for any bad spots, cut them away and chuck them. What is left can be put into a manured hole and banked slightly above ground level so you don't get water pooling on the crowns. Moving roots acts much like pruning does, which will make almost indestructible rhubarb thrive again.  

Thanks a lot for the great advice folks.  Rhubarb Crumble here we come!!