Neighbours cannot prevent work from starting or deny access for you or your contractors if you comply with the terms of the Party Wall Act and the Agreement. However, if you fail to comply with the Act, then your neighbour is entitled to take legal action against you. An injunction can be issued to prevent any further work from taking place until such time as an Agreement is in place. The legal cost of this injunction would fall to you. Neighbours may also seek compensation to redress any losses they have suffered as a result of the works, and worst-case scenario is that a requirement can be sought to remove the work. Unfortunately, Party Wall Notices cannot be served retrospectively, i.e. once the work has been done. There are, of course, circumstances where plans and works need to change…if you have complied with the Agreement then you should be able to simply submit revised drawings and details to your neighbours without having to serve a new notice or renegotiate the Agreement. The Agreement does not override the need for other consents or amendments to other consents, such as planning permission or Building Regulations consent, so always worth checking with your Planning Office and Building Inspector. Whilst compliance with the Party Wall Act undoubtedly incurs a cost, the fees and time are considerably less in the long run than those which could be incurred without it.