My father intends to travel to the UK on a standard visitor visa to go and visit my sister who is married in the UK. He has been to the UK twice before and both times he was issued a visa with no issues whatsoever. When he travelled the previous times he was an abled person but this time around he is disabled. He is an amputee on one leg and even tho he has a prosthesis leg he is unable to walk normally and will require a wheelchair during the journey. On top of that he has kidney issues meaning that he might have to go on dialysis sooner or later. My mother, brother, sister and niece will accompany him. Most of the things he can do on his own and as such doesn't require a carer.
Can he be denied a visa on grounds that he is a disabled and/or a terminally ill person?