My ex husband and l had a really good friendship after divorce , so much so he made a will leaving his bungalow etc to me , His friend ( a women ) he was leaving 15 thousand pounds .he had wrote this will freely , and gave it to my sister too look after for approx 20 yrs , however 18 months ago during Covid lock down , He was told his cancer was now terminal , and that he might have a week or so too live ? His women friend then asked my sister for his will ? She then got a local solicitor too see my ex husband and get him to draw up a new will leaving half of his money too her and her son daughter and grandchildren . I now find the new will gives me 20,ooo pounds , and my son who is 45 the rest of his monies after her family share is taken,  plus my sons inheritance will be tied up in a Trust fund ? I feel this women has been coercive by saying unless he changed his will she would not help him while he was now dying ? 

Do l have a valid claim too over throw this new will ! Made when he was emotionally blackmailed in hispital , where we could not visit him. Due to  Covid ?