Who is Katrice Lee?
Katrice Lee was born on 28 November 1979 at the British Military Hospital in Rinteln.
She disappeared on 28 November 1981 - her second birthday - from a shopping centre near Paderborn in Germany.
The Lee family lived in Schloß Neuhaus, while Katrice's father, Richard Lee, was serving as a sergeant in the 15th/19th King's Royal Hussars in Paderborn.
The two-year-old was born with an eye condition in her left eye, that would have needed two operations to correct.
What were the circumstances of her disappearance?
Katrice went missing from the Navy, Army and Air Force Institutes (NAAFI) shopping complex in Schloß Neuhaus, close to Paderborn.
The family was at a checkout in the NAAFI when Katrice's mother, Sharon, realised she had forgotten crisps.
She asked her sister Wendy, Katrice's aunt, to watch the toddler, but when she returned in what she has estimated was less than a minute, the little girl was gone.
Wendy told Sharon the two-year-old had run after her, and she thought they were together.
The family quickly raised the alarm and searched the NAAFI, shouting out the girl's name.
Watch: Katrice's father described the investigation into his daughter's disappearance as a "complete and utter sham" in 2017.
Both the German police and the Royal Military Police (RMP) carried out an extensive search of the area, with the help of soldiers and volunteers.
The RMP were effectively in charge but had to negotiate with the German police because the NAAFI building was in a German town.
The investigation did not get very far and, despite dragging the local river and conducting house-to-house inquiries, no trace of Katrice was ever found.
German police believed Katrice could have fallen into the fast-flowing River Lippe, near to the NAAFI, which was thoroughly investigated.
However, the Lee family always dismissed this theory, stating that Katrice would not have gone near water.
Mr Lee and his family believe Katrice was abducted and taken as a surrogate child. They have been critical of the initial investigation, which focused on the River Lippe.
He said: "I believe the whole investigation has been a complete and utter sham.
"We felt we've always been a bottom feeder in a fish tank."
Mrs Lee also complained about the investigation, saying: "It took six weeks for the girls working on the checkout on the day that my daughter disappeared to be interviewed and, in one case, it took 20 years for one of those members of staff to be interviewed.
"It took 48 hours for border control points to be informed my two-year-old daughter was missing and it took 24 hours for the sniffer dogs to be brought in to the NAAFI to pick up a scent for Katrice."
The case reopens twice
The case was first reopened in 2000 under the name Operation Bute.
The BBC’s Crimewatch mounted a reconstruction of Katrice’s disappearance, on what would have been her 21st birthday in November 2000.
A suspect was found but was released without charge and the case then closed again.
In 2012, the RMP admitted mistakes were made during the first investigation and the case was reopened for the second time.
The RMP reanalysed information gathered during the initial investigation and identified the River Alme as an area of particular interest.
Watch: A number of e-fit images showing what Katrice would look like at certain ages have previously been released.
A new photo-fit
In February 2017, RMP released a photo-fit of a man that they wanted to speak to in connection to the case.
An eyewitness is said to have seen a man, portrayed in the photo-fit, at the time of the disappearance carrying a small child into a green saloon vehicle.
This image was also released on the BBC's Crimewatch programme.
The River Alme
In April 2018, a team of military personnel and civilian forensic experts announced they planned to excavate a stretch of the riverbank along the River Alme.
A review of the evidence had concluded the riverbank was "significant and of interest".
Senior Investigating Officer Warrant Officer Richard O'Leary said a green saloon car, a main focus of the investigation, was also seen on a bridge going over the River Alme the day after Katrice's disappearance.
Excavation of the riverbank started in early May and was scheduled to take five weeks, but the military said investigators were able to conclude work faster than planned.
The British military announced on 29 May they had ended the renewed investigation after finding no new evidence.
The search of the Alme river banks turned up no new leads on what happened to Katrice Lee, a spokesman said.
Watch: In 2018, Mr Lee said the failed search had only strengthened his family's belief that Katrice was abducted.
On Monday 23 September 2019, the Royal Military Police arrested a person in connection with the disappearance of Katrice Lee.
The man, a former serviceman, was released without charge two days later.
An Army spokesperson said: "The search of an address in Swindon continues and the Royal Military Police are keeping the Lee family informed of developments."
Katrice's father, Richard, said: "This arrest brings it all back and makes it feel raw.
"As with parents in all cases of missing children, we want a happy ending but that might not be the case and we just hope we will get answers."
A woman poses as Katrice Lee online
Heidi Robinson, 40, set up a Facebook profile under the name of Katrice.
Ms Robinson sent a friend request, on Facebook, in August last year to Katrice's sister Natasha Walker.
She continued to pose as the missing toddler, despite the family urging her to take the profile down.
After the DNA test confirmed she was not Katrice, she claimed it was a cover-up.
In October 2019, Ms Robinson was given an 18-week prison sentence suspended for two years with a mental health treatment requirement for 12 months and ordered her to carry out rehabilitation activity for 40 days.