Video report by Rachel Bullock
Richard Lee hasn't seen his daughter in 40 years - but ahead of Sunday's anniversary of Katrice's disappearance, he tells us he still holds on to the hope she is still alive.
The toddler was 2-years-old when she vanished from a supermarket on a British Army base in Germany where her father was stationed.
No trace of her has ever been found.
Speaking to us in his hometown of Hartlepool, Mr Lee says he still holds on to hope his daughter is alive. He believes she was stolen by a childless couple and is unaware of her true identity.
Earlier this month, the Prime Minister agreed to meet Richard Lee 'father to father'. It's after Katrice's case was raised by Hartlepool MP Jill Mortimer at PMQs.
It is something Richard is dubious about.
Downing Street have said the meeting between the Prime Minister and Mr Lee will take place 'in due course'.
Katrice Lee's disappearance
Katrice vanished on her second birthday on 28 November 1981, from the outskirts of Paderborn in Germany, near the British military base where her father Richard was stationed.
She was last seen at a supermarket on the base. There has been little progress in finding out what happened to her.
The Royal Military Police (RMP) reopened the investigation to find Katrice in 2012, with re-analysed evidence identifying the bank of the River Alme in Paderborn as being of particular interest. However, officers excavating a section of the riverbank found bone fragments but they were found to be horse bones and the area was ruled out of the investigation.
In June 2014, another woman falsely claimed to be Katrice Lee, via phone calls in December 2013, only seven months into a suspended sentence for the same offence. Donna Wright was jailed after admitting harassment and breaching her previous suspended sentence.
On 24 September 2019, the Royal Military Police (RMP) made an arrest in connection with the disappearance of Katrice, after searching a house in the Moredon area of Swindon, Wiltshire. An ex-serviceman arrested, then released without charge.