Photo mystery deepens

They have recently been given information about an event that occurred in Sheffield Park a few years before Chris' photo was taken.
Whether what you are about to read, is connected to the image that Chris took, is entirely for you to decide. But one local family is now appealing to Chris to reveal the truth about the image. Was this picture a hoax, sent to us as an elaborate joke, in the hope they would fall for it? If not, the family in question suggest they will have to come to terms with something far more unsettling....
The latest developments occurred when they received details of a tragedy that happened in Sheffield Park on Saturday 4th August 2001. 87 year old Mrs Florence Bristow had gone to the gardens, with her son John and his wife, for an afternoon out.
Once there, they hired a motorised buggy, intending to travel around the edge of the lake. Unfortunately, Florence suffered a heart attack and fell across her son who lost control of the buggy, which then plunged into the water. John's wife dived into the lake in an attempt to save her and although first reports suggested Florence had drowned, later tests showed that she had died before entering the water. Resuscitation attempts were tried at the lake side but to no effect.
Until recently, Mrs Bristows family had not seen Chris' "ghost" picture, but when they did spot it on our website, they were shocked. John contacted us to say he believed the picture "Shows a resemblance to my mother".
Further contact with the family revealed they believe "the lady in the photograph bears a striking resemblance to her [Florence] even down to the type of top she is wearing". John has kindly given us a photograph of Mrs Bristow, with permission to post it here on the website.
So they were asking, is Chris' photo a hoax? His brother Paul, the person who took the original photograph, says it's not! Maybe you know the person in his photo? Could it be you? Were you in Sheffield Park on Sunday May 16th 2004 and can you remember seeing anyone who could possibly be the person in the background? Or is there another explanation for the image?