The interview with the ex-wife was interesting. I think she only spoke up when she found out that Bert Spencer had written a book about it otherwise she'd have kept silent.
When the interviewer asked Spencer how he found out about the murder, he replied "At home. No, the next day at work".
Janet (the ex-wife) said she heard about it at News at 10 on the day of the murder, Bert was in bed and went up to talk to Bert about it, saying "Tell me you had nothing to do with that murder". And he replied "I didn't". How did he know what she was talking about? Most people would say "What murder? What are you talking about?" if he knew nothing about it.
So a huge lie there about when he found out about the murder.
Also, she said he told her that he was going to get rid of his shotgun the day after the killing. He told the documentary crew that he had sold it months beforehand (but he never mentioned that fact to anyone before this).
He also told his wife he wasn't at work the whole day as he was ill.
I think the daughter had it right. Spencer was there at Yew Tree Farm that day (perhaps with Hubert Wilkes to steal antiques), one of them killed Carl, and he later killed Wilkes to shut him up. Otherwise it is an amazing coincidence that Wilkes is killed by Spencer in a very similar way just a month later.