It's the heart-breaking story that moved hardened detectives to tears.

Three babies separately abandoned in plastic bags in freezing temperatures in near identical circumstances several years apart.

For years detectives have desperately tried to trace their mother after DNA tests revealed that incredibly all three children were siblings.

Now, as the two year anniversary approaches of the discovery of the last child Elsa, police are preparing to close the case.

It follows a unique investigation which has taken officers across Britain and abroad using familial DNA analysis to contact possible relatives.

Officers are ready to concede defeat after going to extraordinary lengths and exhausting hundreds of lines of inquiry, the Daily Mail can exclusively reveal.

The investigation initially started in Plaistow, east London, after a newborn baby, named Harry by medical staff, was found wrapped in a white blanket in a bush in September 2017.

Two years later Baby Roman, later found to be his sibling, was found in the same area in freezing temperatures in January 2019, wrapped in a white towel in a shopping bag.

In January 2024, a dogwalker discovered a third baby just an hour old who had been left in a Boots shopping bag in temperatures dipping to -4C.

Baby Harry was found wrapped in a white blanket in a bush in 2017 in Plaistow, east London.

Baby Roman was found in freezing temperatures in January 2019, wrapped in a white towel in a shopping bag in Newham, east London. 

Police image of the Boots bag in which Baby Elsa was found by a dogwalker in Newham, east London, in January 2024.

She was named Elsa after the character in the Disney movie Frozen because of the sub-zero conditions she was found in, but like her siblings, Baby Elsa also survived against all the odds.

Fearing that it may not be long before a fourth child was discovered, police vowed to do 'everything possible' to find the children's mother.

Detective Inspector Jamie Humm and his team of 15 officers started by scouring 450 hours of local CCTV, but they found no trace of either parent.

Police believe the infants were abandoned near the Greenway, a footpath in Newham built over a sewage pipe, because there was no CCTV there.

'How can you have the most surveilled city in the world and someone drop three babies off without being identified?' Detective Humm said.

'It was chosen, I would argue, as a fairly optimum location of making sure the babies were found relatively promptly whilst also giving the mum the most opportunity for a covert entrance and exit.

'It is a footpath - there are no shops, there was no dash cam footage from passing traffic, no doorbell camera.

'So, from that point in your investigation, you are effectively looking for a ghost, someone who's been and gone without ever having left a trace.'