It’s a fact that, if you are an allotment tenant (i.e. you have a tenancy agreement signed by yourself and on behalf of Bolton Council), you are the legal possessor of the allotment and you’ll have a duty of care under the Occupiers Liability Act 1957 (and the 1984 Act in relation to trespassers).
What this means is that you need to assess all potential hazards on your allotment and ensure that you remove anything that may be a danger to visitors (and trespassers) on your allotment. If a visitor verbally (or in writing) accepts the risk to themselves while on your site, then, you will have no liability, however you cannot put a sign up like “I accept no liability for vistors safety” etc. Trespassers (e.g. burglars), could sue you if they are injured in the act of robbing from your allotment, but, this happens rarely (if at all).
So, the risk of being sued for visitor accidents on your allotment is slight, but, some allotment holders don’t want to take the risk and feel safer if they have liability insurance. If you Join the National Allotment Society (https://www.nsalg.org.uk/), then you’ll get liability insurance as part of the membership fee (currently £23 for a single membership). You can get membership of the National Allotment Society cheaper if you can get 10 or more allotment holders to join together in a block membership deal. This costs just £3 per membership, and liability is included. You’ll need to provide your contact details to the National Allotment Society for the liability insurance to be valid, and, remember, this insurance doesn’t cover theft from sheds etc. just visitor and trespasser accidents.
If you’re interested in forming a group to get the discounted membership, then email me, Ian Bullough, Secretary, Sapling Road Allotment Society at secretary@saplingroadallotmentsociety.co.uk