The couple, who wish to remain anonymous, told BBC Radio 4's PM programme that on the night of the murder in August 1961, they had seen a man standing beside a Morris Minor in the lay-by at Deadman's Hill in Bedfordshire, where Mr Gregsten was killed and where Valerie Storie was sexually assaulted and shot. She survived the attack but has been paralysed ever since.
The man and woman said yesterday that the man they saw that night looked nothing like Hanratty. The woman described how she wound down her car window and asked if the man wanted help or if he was in trouble.
"He [by now inside the car on the driver's side] was very abrasive, he leaned over to the passenger side, almost to the dash, and at that we felt that no, he didn't want our presence so we drove on," she said.
The woman added that they both made statements to the police the day after the crime which were not followed up.
"I feel it's just very sad that no one took any notice of our statements and, in such a serious incident, it was a man's life, which must be important. Very sad," she said.
The man added that when photographs were published of James Hanratty, they felt that the person they had seen that night did not bear any resemblance to him but did bear a strong resemblance to the police Identikit picture.
"It's just really bugged us, haunted us over the years, when we think of what's actually happened.
"It's a case of, really, `if only'," he said.
A subsequent Scotland Yard investigation is understood to have concluded that there was a miscarriage of justice and that the wrong man was hanged. The Home Office are about to publish their review of the case which is also thought to confirm that Hanratty was mistakenly executed.
Hanratty always maintained his innocence and his family and friends have campaigned to clear his name.
However, a former trial juror said last night the jury made the right decision based on the evidence presented to them.Reuse content