According to Official Guinness Records,
Only fruit and vegetables grown primarily for human consumption will be considered for publication. Documented claims for agricultural crops and animal fodder produce such as sugar beet and mangolds are welcome, but these will be dealt with separately. Priority will always be given to items entered and measured at officially recognized horticultural competitions, shows and events, where designated qualified judges are present. The competitions can be at local, national or international level, but copies of the competition rules should be supplied with the record claim. In case of practical difficulties in getting to shows, it may be possible to arrange for judges to assess claims at the actual growing site. Claims from the UK must be authenticated by National Vegetable Society or Horticultural Society judges as appropriate. Claims from overseas should be authenticated by suitably qualified national equivalents. All entries must comply with the rules of the show/competition. Where the rules of the show/competition differ from our own, we will nominate an independent witness to see that the fruit/vegetable is eligible for inclusion in the book. In any case, we reserve the right to have the specimen examined by an expert nominated by us. All claims should be made as soon as possible after judging. Generally speaking, retrospective claims will not be considered for publication unless the circumstances merit it or they are particularly interesting for historic or other reasons. To minimize delays and administrative problems, claims should ideally be submitted by the actual grower(s) rather than by a third party. The following should be provided signed and dated statements from the show judges and those responsible for weighing and measuring, with contact addresses and telephone numbers. Where applicable, completed and signed copies of any official entry forms should also be provided. The species and variety should be clearly stated. If possible, scientific names should also be given. Two further signed statements of authentication by independent persons of some standing in the community or by representatives of a relevant organisation (which could be the gardening press), including contact addresses and telephone numbers.
For a complete list of 2018 records, please visit 2018 Guinness Records in United Kingdom.