I don't know what William's father was called.I have the certificate for his first marriage to Emma Lambert. I was so dissapointed when it arrived as it gives no name or profession for either father, it just says deceased. I have a birth certificate for a William Gravell 22/10/1849 born at the Union Workhouse, Grays Inn Lane.Parents are Alfred and Susan(neé Moore).The year and place fit with the information given on the 1901 census but I have nothing conclusive. It is very frustrating.
If you post on the London page, sombody might search the 1851 census for that address which might help. I saw from your other posting that there was a connection with one of your ancestors, what was their name?It might be one connected with the family in some way.