Should marriage revoke a Will?

Predatory marriages seem to be on the increase, as in this desperately sad case, the vulnerable person often has dementia, and would not have capacity to make a Will, yet are able to marry. 

So what is the answer? Should marriage no longer revoke a will? Or should there be more training for registrars who apparently assess capacity before the marriage takes place. Or perhaps a new basis for annulment of the marriage post death in circumstances such as these, where presently it must be bigamy or incest.

An incredibly sad state of affairs and it feels criminal that this individual got away with it because it wasn’t considered a ‘forced marriage’.

Daphne Franks: the woman who lost her much-loved mother to a predatory marriage
Joan Blass was 87 and had dementia when a man befriended her, then married her quietly, inherited her estate when she died – and buried her in an unmarked grave. Now Franks works tirelessly to make such marriages a crime .
According to Daphne Franks, her mother was 87 when she met Colman Folan. He passed by when Joan Blass was trimming her hedge, the two got talking and she invited him in. Even this was out of character for Blass, says Franks, who lived about 30 metres from her mother in Leeds. She would once have been a bit more cautious, but Blass had been widowed three years earlier and diagnosed with vascular dementia.