I would recommend a completely different approach to most and which I believe is the way to go. Set out expecting to catch nothing. Talk to as many anglers as possible on the bank asking their advice and in return make some suggestions on how they could improve their fishing. If you happen to see someone catching, find a swim close by so you can see what they are up to. Wander over every so often and have a general chat, for example, what you and your mates get up to, memorable holidays that you have had, your hobbies, what make of flask that they use etc. In between, glean what knowledge you can, ask if they would mind giving you a sample of their bait. You will find that most barbel anglers in this situation will be very helpful. If not, bring your fishing chair over and settle down for a decent chat. Most anglers respond favourably to this approach. Offer to help with any landing of fish. Don't be fooled by the suggestion that there is a red hot swim somewhere else on the river. Ultimately, they may be kind enough to pack up and vacate their swim for you. If you blank then you go home not being disappointed and if you do happen to catch, well, that's a bonus and in the process you've probably made a friend on that stretch of the river.