Dd1 has a (new to her) small Beinn 20. It obviously needs a decent lock given how much it cost even secondhand, but on the other hand I don't want anything really heavy as the main point of that bike is it's lightness.
I would like to be able to leave it at the swimming pool, but DH had his (chained, not D locked) bike nicked from there recently. Is there any lock that would be really secure but not too heavy? Ideally with a number combination as otherwise we will have key issues.