Celebrations to mark the 750th birthday of Britain's tallest cathedral will come to a climax tomorrow when the Archbishop of Canterbury dedicates its exquisite new font.

Hailed as a 21st-century masterpiece, Salisbury Cathedral's first permanent font for more than 150 years is the culmination of 10 years work.

Designed by distinguished sculptor William Pye, the font is now fully installed and gleaming with water. It is also one of the largest pieces of modern art ever installed in a medieval cathedral.

As part of celebrations the Most Reverend and Right Honorable Dr Rowan Williams will also rededicate the majestic cathedral – exactly 750 years since the then Archbishop of Canterbury dedicated the newly completed structure in 1258.

And there will be emotional moments for two families as Dr Williams will baptise two babies in the font. They will be Rose Eleanor Price and Beatrice Emilia Peony Bowen.

The Dean of Salisbury, the Very Revd June Osborne, said: "This new font is a masterpiece. Now we see it in its permanent position in the middle of our magnificent medieval cathedral, it is even more beautiful than we could have imagined.

"It is so right for the building, a real 21st-century treasure, both contemporary and timeless.

"It is deeply significant that it will be formally dedicated for us and used for baptism for the first time by the Archbishop of Canterbury when he leads our worship on Sunday during our 750th anniversary weekend."

Fittingly it was the dean – now one of Britain's leading churchwomen – who instigated the project for a new font a decade ago when she was the cathedral's canon treasurer.

She and her colleagues believe the font is the most significant addition to the fabric of an English cathedral in recent years.

Cruciform in shape and with a 3m span to allow total immersion baptism, it is a green bronze vessel with a Purbeck Freestone plinth and brown bronze grating.

The Salisbury Font has streams of water flowing from its four corners while a perfectly smooth, still surface of water reflects the surrounding architecture of the cathedral.

Canon treasurer, Mark Bonney, responsible for the fabric of the cathedral, said: "For the first time in almost 200 years the place where baptism is administered will reflect the importance that we, as Christians, attach to it.

"Its location near the entrance to the cathedral is a very powerful symbol, reminding us of our own journey through life, of pilgrimage and discipleship."

He said the words engraved on the four curves of the font were taken from baptism and confirmation services that the Bishop of Salisbury, Dr David Stancliffe, was instrumental in creating.

Taken from Isaiah, chapter 13, verses one and two, they read: "Do not fear for I have redeemed you. I have called your name, you are mine. When you pass through the waters, I will be with you. And through the rivers, they shall not overwhelm you."

Mr Pye said: "The Cathedral's brave move to procure a font with flowing water has meant that I have been able to design a piece that accentuates the beauty of water as a medium to reflect the beauty of the building within which it resides.

"I hope that it will be seen as something timeless that has been absorbed naturally into the fabric of this great building."

"It has been a privilege to design and create a piece which will now form an integral part of this wonderful cathedral and its history."

Arts journalist and author Simon Tait said: "William's extraordinary water pieces adorn gardens, squares, galleries and great houses, but this font is probably his most important piece to date.

"Not just for where it is but for the way he uses his artist's eye to make it do the job it does. It's a very beautiful church piece."