A man has been sentenced to five-and-half years in prison after being arrested on explosive charges in the lead up to the visit of Britain's Prince Charles last year.

Donal Ó Coisdealbha, 25, from Abbeyfield, Killester in Dublin admitted being a member of a dissident republican organisation.

During today’s sentencing hearing, Ms Justice Isobel Kennedy criticised as "puzzling" a letter written by Independent TD Maureen O Sullivan to the courts on behalf of the Real IRA member.

He was arrested during a Garda operation which recovered explosive devices, improvised rockets, detonators, timing units and Semtex, six days before the visit of Prince Charles and his wife Camilla to Ireland in May 2015.

Ó Coisdealbha was held as part of a Garda investigation into the activities of dissident republicans.

He had been under audio and visual surveillance for five months and was seen meeting convicted IRA members in the Coachmans Inn near Dublin airport and The Pint pub in Tara Street in Dublin city centre - as well as acting suspiciously at the back of Glasnevin Cemetery.

He was also seen buying clingfilm and driving to a house at Harbour Court in Wexford.

When the house was subsequently searched, four improvised rockets, a booster tube, five phones, Semtex, homemade explosives, a timing power unit, a broken circuit board, a cord of cortex and two detonators were found.

Officers from the Special Detective Unit then searched his locker at NUI Maynooth and discovered a timing power unit and a circuit board, which fitted together with those found in Wexford.

Detective Inspector William Hanrahan had told the court it was clear from the conversations recorded, about a bike and detonators having been obtained for Ó Coisdealbha, that preparations were well advanced.

He was told that it was his operation and they were ready to go.

Gardaí believed that the operation was to take place around 19 May 2015 when Prince Charles was visiting Ireland.

There was a reference to a timer with a 14-minute delay and the blame to be given to a different IRA organisation and this caused gardaí to move in on 13 May - six days before the visit.

The court heard that Ó Coisdealbha is a single man with no previous convictions. He is educated to third-level and works in biomedics and lives at home with his parents.

His defence counsel said his guilty plea was a public acknowledgement of his wrongdoing.