I would say that if it was caught in summer after spawning at around 18lb+, then possibly every chance it would be near to breaking the british record the following year, if the barbel is still healthy, eating, recovering ok and not too old. If the barbel was/is caught around this time in winter at 18lb+ then it may only put on ounces if there are very cold water conditions. Generally, lowest weight after spawning, mean weight around october, max weight at the back end of the season or in the close season before spawning again....if the fish is still capable of spawning. It all depends on the river and weather conditions, health and whether the barbel still has the built in potential to grow on a bit more and put on a bit more weight. In my experience, some do and some don't to where some drop weight and some just stabilize around the same weight, just fluctuating up and down by ounces. Very cold water conditions can make them very inactive or semi-dormant to where they lay up and possibly live off their body fat for a period of time, and don't necessarily go out and about looking for food items to any degree....in my opinion..