The 92-year-old monarch adopted the dog after Fenwick's death despite saying she didn't want any more canines, fearing that she would leave behind a young pup following her death.
Although she still has two dogs, Candy and Vulcan, they are dorgis, dachshund and corgi crosses.
Queen Elizabeth is said to be devastated after her last corgi has passed away. "The Queen thought it was a bit obscure and preferred the proper spelling". Willow was the last in a 14-generation line of corgis descended from the queen's original corgi, Susan.
Bill's wife Nancy died three years ago and according to reports, she used to look after the Queen's dogs.
This has been a hard year for the queen, who lost Willow just six months ago.
"She couldn't resist Whisper and now she has asked Bill's family if she can keep him", a source told The Sun past year.
She anxious about tripping over excitable puppies, and was concerned about who would look after them when she no longer could.
Vets were called in last week while the Queen was at Windsor Castle after the wedding of her granddaughter Princess Eugenie.
Buckingham Palace declined to comment when contacted by Sky News.
The Queen loves her corgis!
"It really does feel like the end of an era", palace sources told the Daily Mail's Richard Kay at the time of Willow's death.
First introduced to into the family by the Queen's father, King George VI, in 1933 with a corgi named Dookie, the furry friends quickly became synonymous with the Queen, who was often seen traveling with them or with the four-legged friends following closely behind her. Follow Yahoo Lifestyle on Facebook, Twitter and Instagram.