Am amazed it didn't flower, as these are tough 'wild' roses that usually form a lovely hedge, much loved by council's everywhere!! Don't cut it down too hard, just trim off the excess before March. I have taken a hedge trimmer to this one with no adverse results, as long as I didn't cut into the old wood. If the plant needs thinning, then cut any of the older wood down to the base. Perhaps it is water-logged? Also, don't feed a high nitrogen based feed, if at all.