Max Wall, 18, became unwell as he was about to board a ferry on the holiday island and was found unconscious in the port area on Sunday afternoon.

Just hours earlier on Sunday morning, the body of Andrew O'Donnell, a fellow pupil at St Michael's College in south Dublin, was discovered on a rocky ground.

Mr O'Donnell, also 18, is believed to have fallen on his way back from a night out on Friday.

Greek police are looking into the circumstances of the teenagers' deaths, with Irish police flying into Ios to assist the investigation.

Both teenagers were among a larger group of students from St Michael's College and other schools in Dublin, who flew to Ios to celebrate their Leaving Certificate exams finishing.

Friends and family gathered at the Church of the Sacred Heart in Donnybrook, Dublin, on Monday to pay their final respects to Mr Wall.

The teenager spoke to his father on the phone in the moments before his death, the service was told.

Niall Wall said his son was "full of life" and "brightened the life of others".

"Today marks the end of an eight-day journey for us that with the most profound cruelty has not only taken Max from us but has robbed him of a bright future.

"He was the best craic. He was full of fun. The best kind," his father added.

"The most important thing about Max is that he simply was our fabulous son and we will love him forever."

He also offered his condolences to Mr O'Donnell's parents, Bebhinn and Gavin, revealing how they had formed "the closest of friendships" through their "nightmare" joint journey.

Mr O'Donnell's funeral will take place at the same church on Wednesday.

Mrs Wall read the poem Funeral Blues by W.H Auden before describing her "darling boy" as a "force of nature".

"Your memory will live on," she said.

Objects to represent Mr Wall's passions, including a Manchester United shirt emblazoned with his name, a signed Leinster rugby jersey and a pool cue, were placed at the front of the church.

His parents took religious symbols forward to represent his strong faith while his brother, Charlie, delivered a reading.

St Michael's College chaplain, Fr Paddy Moran - who celebrated the graduation ceremony attended by Mr Wall, described the event as a "joyous occasion".

Leading the funeral service, he told the congregation: "I looked out at this sea of faces ready to embark on the next stage of their lives as young adults - young, energetic men ready to take on the world.

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"It never occurred to me that we would be gathered two months later for the funeral of Max.

"It is heartbreaking to be gathered in this most tragic of circumstances.

"Our hearts are broken."

'Devastating loss'

St Michael's College said the deaths of Mr Wall and Mr O'Donnell was a "devastating loss", with students left "absolutely traumatised" by the tragedy.

The school hailed Mr Wall as a "constant source of positivity" while Mr O'Donnell was described as a "popular classmate and friend" and a "proud and committed member of our football team".

Mr Wall was "extremely popular with staff and students alike, and a fantastic supporter of our teams during the various cup campaigns".

He was also a "great brother" to Charlie, a past pupil at St Michael's, the school said.