[robinahood]

I have read that beans like something moisture retentive at their roots. I grow borlotti and broad beans without providing this, other than a little compost, on light soil, and am happy with the results, but if I could increase my yield so much the better! What do you think works for you when preparing the trench? I would be grateful for  your comments. Thanks!

[beesrus]

The moisture thing you refer to is more for Summer beans, which of course includes Borlottis. Runners are the main Summer beans that benefit from moisture retention, along with French. It's not so important for your Broad beans as they are sown in early Spring when moisture shouldn't be much of a problem.
The classic trench method for runners/borlottis you refer to is leave it open, and keep tipping your raw vegetable peelings into it, maybe some shredded non coloured newpaper/thin cardboard, but don't put in potato peelings for obvious reasons. Then just keep sprinkling soil over and gradually fill up over Winter. Simple.

[robinahood]

Thankyou, that certainly sounds doable. I will start that once the space is free.