The mother of toddler Ben Needham, who went missing 21 years ago on a Greek holiday island, has said she supports a major new search operation aimed at finding her son which is beginning on Friday.

A team of British police officers and search specialists arrived in Kos this week to help a Greek investigation which will focus on a large mound of earth and rubble close to where Ben was last seen.

His mother, Kerry Needham, has always believed her son is still alive but admitted on Friday the new operation had planted doubts in her mind.

Ben, from Sheffield, vanished on the island in July 1991, when he was 21 months old, after his mother and grandparents, Eddie and Christine, moved there to renovate a farmhouse.

Despite a number of possible sightings and a range of theories about what happened to him, no trace of the youngster has been found.

The British team, led by Detective Superintendent Matt Fenwick, of South Yorkshire Police, is understood to be about 18-strong and includes dog teams and a forensic archaeologist.

Their search will focus on the grassed mound which is near a farmhouse next to the one Ben's grandparents were renovating in 1991 and where the youngster was last seen.

One theory is that it is building material which was dumped at the time the toddler went missing and the youngster could have been accidentally buried beneath it.

But Mrs Needham has said in previous interviews she believes the large mound was already there when Ben disappeared.

Earlier this year, she said: "I find it very, very unlikely that Ben is there, unless he buried himself."

Now Mrs Needham has said she is supporting the search, despite her belief her son is not buried under the mound.

In a statement, she said: "Just over a year ago I visited Kos and spoke to the Greek Prosecutor and the Chief of Police for the island.

"They promised me they were serious about reinvestigating the disappearance of my son Ben.

"I am so pleased that this investigation is now moving forward and that the Greek authorities are showing a true commitment to investigate Ben's disappearance.

"My family have been updated and supported throughout this time by officers from South Yorkshire Police and as a family, we are so pleased that the Greek authorities have allowed the team of experts led by Detective Superintendent

Matt Fenwick to assist them with the search.

"Today is just a start. I understand that all possibilities have to be considered and the search of the area around the building work where Ben disappeared is part of that."

In an interview with the Daily Mirror, Mrs Needham said: "I know in my heart of hearts they will not find Ben there because he is still alive somewhere. But I have to admit for the first time ever this search has put doubts into my head."

She said she will be travelling to Kos, adding: "It is the last place I want to be but I feel I need to."

The police operation will begin with a specialist survey using hi-tech geophysics equipment.

The team is not planning to begin digging straightaway, it is understood.

Loading Slideshow

• h_50563357

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563356

  Greek and British police officers are to inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563355

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563354

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563353

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563352

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563351

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563350

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563349

  Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• h_50563348

  Greek and British police officers inspect a field where a bulldozer is set to dig up a mound of earth to try to find the remains of Ben Needham on the island of Kos Greece 19 October 2012. Ben was 21 months old when he went missing on the Greek island of Kos in July 1991 close to an old farmhouse which was being renovated by his grandparents. A British team of expert searchers led by South Yorkshire Police has travelled to Kos and will begin examining the ground around the house in order to excavate the mound. The operation which is expected to last between a week and ten days follows a request from Greek police for specialist support to follow up one of their lines of inquiry South Yorkshire Police

• Crime - Missing People - Sheffield

  Mrs Kerry Needham with a new computer picture of her missing son Ben at a police conference in Sheffield.

• Ben Needham missing

  Undated file handout photo of toddler Ben Needham, who went missing 21 years ago on Kos, a Greek holiday island, as a team of British police officers and search specialists arrived in Kos this week to help a Greek investigation which will focus on a large mound of earth and rubble close to where Ben was last seen.

• How missing Ben might look at

  Undated National Missing Person's Bureau handout photo of a digital created image of Ben Needham and how he is expected to look now aged 18. Ben was last seen 16 years ago, and this image has been released to coincide with his eighteenth birthday.

• PNR 18 15.1.95. SHEFFIELD. UK PROVS USE ONLY, ALL TV, FOREIGNS, NATIONALS (INC REGIONAL EDS) OUT. One of the pictures taken las...

  PNR 18 15.1.95. SHEFFIELD. UK PROVS USE ONLY, ALL TV, FOREIGNS, NATIONALS (INC REGIONAL EDS) OUT. One of the pictures taken last August by holidaymaker Doris Bell on a Turkish beach, which show a boy who resembles missing toddler Ben Needham. Ben, 5, vanished in July 1991 during a holiday in Kos at which time he was only 14-months-old. Although police received the pictures and a video from Mrs Bell in August, his mother Kerry, 23, from Sheffield, was not informed of their existence until a week ago. PA News. See PA story POLICE Needham. /PJ.