I posted this story a few years ago, but here it is again - a friend of mine was made redundant and got a job as a security officer at Hatfield House in Hertfordshire.
He worked the afternoon shift and one part of his job was that every so often he had to walk round a prescribed route around the house and grounds and 'clock in' to the time clocks. He got to know most of the staff that works there and as he walked through the gardens, he would sometime see one of the old gardeners pottering about in the flower beds. My mate would nod, the gardener would smile back. One day one of the archivists/librarians asked my mate to give her a hand to carry some old boxes of photos from an attic room to her office. She was going through them to put on a kind of 'upstairs - downstairs' display. As my mate looked through the photos he saw a group shot of gardeners, one of which was the old boy he nodded to. He pointed to him and said 'He hasn't changed much'. The librarian told him he must be mistaken as the photo was taken in the 1920's, and all the old gardeners on it would be dead by now.
He hasn't seen the old boy in the garden since. Now my friend is not someone who believes in ghost, he still doesn't, but he swears blind what he saw, and says there must be an explanation - he just can't think what it is.
To be honest Herts is well know for a long tradition of inbreeding so if your friend had claimed to see a three headed gardener it wouldn't have surprised many, simply seeing somebody who looked like his grandfather/uncle/Cousin etc is not really that shocking....