Doesn't need a warden, requires the info to be passed on to the Environment Agency so they can deal with it -
http://www.environment-agency.gov.uk/homeandleisure/recreation/fishing/118730.aspx
How to report illegal fishing
Spotted something that doesn't look right? Help us to stop those damaging our sport, If you see any fishing, netting or trapping your think is illegal, please don't tackle it yourself.
Call us on 0800 80 70 60 and tell us:
1. Exactly where the alleged offence is
2. What's happening
3. How may people are involved and a description of them
4. The registration numbers of any vehicles
Please leave a contact number so we can call you back.
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Used to be that anyone holding a fishing licence could show it to anyone else fishing and ask to see theirs - not that these characters would have a licence or be more likely to reply with a bop on the nose!