Difficult to understand that the owners of the land currently being searched took two years, after a study into the terrain and surroundings, to pass on the information (whatever it is), to the police. Unless information was passed on initially but it's taken updated forensic science to evaluate it. Having submitted a file requesting prosecution to the CPS, with regards to the "four" arrested, and the CPS not charging anyone due to lack of evidence, it's obvious that the police have evidence of a Crime and knowledge of a crime, but that it's not strong enough to guarantee a 90% chance of prosecution, and that it may be reliant upon circumstantial evidence rather than weighted in factual scientific evidence..... also known as 'proof'. The police will have had all CCTV material analysed by experts, and will have 99% for sure, seen and noted everything that has been and is being discussed on here. Police tactics throughout the investigation have obviously been carefully planned and organised with aims and objectives in mind.