The actor admitted he had 'shed a tear or two' when reflecting on happier times with Dorrie and will always be grateful to have shared a part of her life.
He added on the Instagram post: '98 years and I'm so glad I got to be a part of them and as I lie awake pondering and knowing that she too will pass soon now perhaps before I wake I pray I smile.
'I shed a tear or two at the memories of Sunday lunch with Yorkshire pudding (she made the best) and roast potatoes and beans from the allotment and pudding and humbugs and walks in the fields or alone the canals and knitted cardigans the love and history I am so grateful for my grandma Dorrie I love you.(sic)'
In the comments of his post, Orlando was given some support from his girlfriend Katy Perry. She wrote: 'Love you angel.'
His post comes after People Magazine claimed the actor is interested in making it last with the 33-year-old songstress by popping the question.
'Orlando doesn't have a ring yet but has been talking about the future,' said a source. 'Everyone would be excited if they got engaged. Katy is wonderful!'
And he thinks she would make a great wife. 'He always said he would absolutely get married again, and it seems Katy could be it. They both seem very happy,' said the friend.
This is round two for Katy and Orlando who first got together in January of 2016. They stayed together for a little over a year before splitting in February 2017, but then resumed their relationship in April of this year.