Adam in one sentence you are asking did Jeremy not have a key to WHF next sentence you are saying he did not have a key to WHF. We discussed this with you earlier try and remember what was posted only two keys to the new door one held by the parents the other by Barbara Wilson. The reason the rellies had a key to the farm is because after the murders Jeremy gave them his key and this was how they managed to get in looking for evidence
in and out of the farm via a window Jeremy told the police he often accessed the farm this way if his parents were not there. Do you not read our posts.
Neville & June did not give Jeremy a front door key.
After the deaths WHF was Jeremys. He used it to enter & exit as he pleased & let in valuers for the items inside. If he needed to gain access after the murders, either use his own keys or get them back from the relatives. Did he not have a spare set ? If the police had the keys, ask. Why use a hacksaw after the murders ?
Perhaps he used the hacksaw before the murders & was making sure he could get a quiet entry prior to the murders ?