Ben Roberts-Smith's twin teenage daughters were 'hysterical' after watching their father being arrested in front of a planeload of passengers and escorted off a Qantas flight by federal cops.

The 15-year-olds were put into a vehicle and not told where they were being taken, according to an account of the traumatic event given by their grandmother. 

The sisters had flown from Brisbane to Sydney with their father and his partner, Sarah Matulin, for what was supposed to be a surprise shopping trip for the Easter school holidays.

What happened next was described by Roberts-Smith's mother, Sue, in an email she sent to family and friends hours after her son was taken into custody and charged with war crimes.

The Daily Mail has confirmed the authenticity of the email.

Among the note's recipients were former members of the SAS, the regiment in which Roberts-Smith served in Afghanistan, where he was awarded the Medal for Gallantry and the Victoria Cross.

Roberts-Smith, his parents, Ms Matulin and the two girls had a family breakfast on the morning of April 7 as part of what Mrs Roberts-Smith described as a 'lovely Easter'.

'...The girls were going to a surprise destination with Ben and Sarah because they were on holiday,' Mrs Roberts-Smith wrote. 

'They were to have a day of shopping in Sydney, because they are 15 and they love shopping.' 

Roberts-Smith, Ms Matulin and the girls boarded their flight in Brisbane and took off.

'When the plane arrived on the tarmac in Sydney, the passengers could see police cars with blue lights flashing and numerous uniformed and plainclothes officers standing there waiting to meet it,' Mrs Roberts-Smith wrote.

'The police boarded while all the passengers were still in their seat belts. 

'The police went straight to Ben, they told him in front of all the passengers that he was under arrest and escorted him, Sarah and the girls off the aircraft.'

Also waiting to film Roberts-Smith's arrest were representatives of Nine Entertainment, which had first accused him of committing war crimes in 2018 in a series of articles written by Nick McKenzie and Chris Masters.

'My understanding is that Nick McKenzie was given a heads-up before it happened,' Mrs Roberts wrote in her email. 'Why?'

Mrs Roberts-Smith said her granddaughters and Ms Matulin were 'distraught'.

'We received a phone call from Sarah who said, "I am in a police car with the girls, Ben has been arrested, the girls are hysterical,"' she wrote. 

'She was very distressed. She then said, "We don't know where they are taking us and we don't know what is happening to Ben!"

'She was unable to speak with Ben. Apparently, Ben was very calm through this whole public display. His only concern was for Sarah and his daughters.'

Roberts-Smith was taken to nearby Mascot police station where he was charged with five counts of 'war crime - murder' allegedly committed in Afghanistan's Uruzgan Province between 2009 and 2012.

The 47-year-old is accused of shooting dead one unarmed Afghan detainee, jointly murdering another with a fellow SAS soldier, and ordering subordinates to execute three more.

Roberts-Smith, who was granted bail and is living on the Gold Coast, has denied any involvement in unlawful killings or other war crimes. 

His arrest was the culmination of a five-year joint investigation by the Australian Federal Police (AFP) and the Office of the Special Investigator (OSI).

The OSI was established following the 2020 Brereton Report which found 'credible information' that 25 Australian special forces personnel had been responsible for 39 unlawful killings in Afghanistan.

The Mail previously revealed Roberts-Smith had repeatedly offered to surrender himself at a time and place of the AFP's choosing if the agency intended to charge him with any offence.

'The AFP could have arrested BRS at the BNE airport [Brisbane Airport] without the flashing lights and the large police presence when they touched down in Syd,' Mrs Roberts-Smith wrote.

'Obviously, they want this to go back to the NSW Courts despite him living in Brisbane!'

There has been widespread speculation about why the AFP chose to arrest Roberts-Smith in NSW rather than Queensland, and where he would face the best chance of a fair trial.

NSW no longer runs committal hearings at which the prosecution brief is weighed by a judge to determine whether there is sufficient evidence to put a case before a jury, whereas Queensland still does. 

When Roberts-Smith made a bail application 10 days after his arrest, the Commonwealth Director of Prosecutions submitted that he represented a flight risk if released from jail.

Mrs Roberts-Smith said that since war crimes claims against her son were first raised in 2018 and 'constantly reported on by Nine and other media', he had 'travelled overseas on numerous occasions and always returned to Australia'.

'He did so in the full knowledge of the reports of investigations into allegations by the AFP and OSI,' she wrote.

As a result, Roberts-Smith had undertaken to surrender himself 'to avoid trauma to his family and a media circus which would have the potential to impact on the conduct and fairness of any trial which might follow'.

Two days after Roberts-Smith was released on bail, he described his arrest as an 'unnecessary spectacle' while delivering a statement to media on the Gold Coast.

'For the past 10 years, my family and I have been subject to a campaign to convince Australians that I've acted improperly in my service in Afghanistan,' he told reporters, as Ms Matulin stood by his side.

'As I've always maintained, I categorically deny all of these allegations, and while I would have preferred these charges not be brought, I will be taking this opportunity to finally clear my name.

'I'm proud of my service in Afghanistan. While I was there, I always acted within my values, within my training, and within the rules of engagement.'

Roberts-Smith said he was proud of the Australians he had served alongside in Afghanistan and asked that their service not be forgotten, particularly those who had made the ultimate sacrifice, 'many of whom were my friends'.

'I'd like to thank my partner Sarah, my beautiful daughters, my mother and father, and all of Sarah's family for their unwavering support, for standing by me during this difficult time,' he said.

'I'd also like to take this opportunity to thank the millions of Australians who have reached out to me, publicly and privately, to offer their support and well wishes. It means a great deal to me and is extremely humbling.'

Roberts-Smith understood his case was 'unprecedented' and had attracted huge public interest.

'But I would ask that the media please allow my family their privacy at this time, particularly my children, who have already unfortunately suffered through a deliberate sensational arrest that was made last week,' he said.

'An unnecessary spectacle. 

'I understand this journey will be long, I understand this journey will be difficult, but I can promise everybody that I have never run from a fight in my life.

'I will never give up and I will always be in the fight.'

Roberts-Smith was named Australian Father of the Year by The Shepherd Centre, a children's charity, in 2013.

He separated from his daughters' mother Emma Roberts in January 2020 and they divorced in February 2021. Roberts-Smith has been in a relationship with 34-year-old Ms Matulin since late 2020.

Ms Roberts, who dropped the 'Smith' from her surname after the couple split, gave evidence against her former husband in his defamation case against Nine.

The AFP and the OSI have refused to answer questions about whether Nine was tipped off about Roberts-Smith's arrest. Nine has also declined to comment. 

Roberts-Smith has been excused from attending when his case is next mentioned on June 2 in Downing Centre Local Court.