Please, help me to ascertain if this autogragh of Freddie Mercury authentic or not?

I've purchased the autograph with the COA several months ago from Ireland. The seller, an experienced collector, UACC member, says the photo was signed in February of 1988 in Garden Lodge, Kensington, London. The item is a coloured gloss photograph sized 12"h x 8"w signed with a green sharpie.

I found out that professional photographer Phil Dent took this unreleased photo (which is very rare on the net) on July 01, 1986 on Wembley stadium. Mr. Dent had the kindness to talk to me. He says he doesn't remember if he produced any prints within the first two years after the concert, but he can't be sure and therefore couldn't say if the signature is genuine or not.

As far as I know Freddie used a green sharpie for writing notes on that time and did signed his photos for his fans in Garden Lodge (there's the video on the net).

Still I can't say for sure if this autograph authentic or not. Any opinions are welcome. I will be grateful for any help.

P.S. The colours of the photo differ a bit from the original after I have scanned it.