Kiruba Ranjit is excited " but perhaps a little nervous " about standing up before the Queen, world leaders and a live TV audience this afternoon to pray to her God.

Kiruba, 15, whose family migrated from India in 1999, is one of two young people who will lead the congregation in prayer during a Commonwealth service at St Andrew's Cathedral from 12.30pm today.

Her audience will include Queen Elizabeth II, the Duke of Edinburgh and the Earl of Wessex, Prince Edward.

The royals, together with representatives of Commonwealth nations, the Prime Minister John Howard and Australian community leaders will attend the Commonwealth Day observance to marks the opening of the Melbourne 2006 Commonwealth Games.

It is the first time it has been held outside Britain.

Kiruba's prayer has been written by the Dean of Sydney, Phillip Jensen who wrote and will lead the service.

Archbishop Peter Jensen will preach the sermon.

Family from a "humble background'

The teenager, who attends Strathfield Girls' High School, is a member of Sydney’s growing Indian and Subcontinent Anglican community.

Originally from the coastal region of Chennai, her parents are both teachers and the family attend St Anne's, Strathfield, where Kiruba teaches a Sunday School class.

She has won a number of awards for singing, and sings in local churches in her native language, Tamil, as well as in English.

Evelin Ranjit, Kiruba's mother, says she is thankful to God that he can be honoured in front of the Queen and world leaders.

"We are from a very humble background," Mrs Ranjit says.

"It’s a privilege for my daughter - we are so happy and so excited."

Veteran photographer gears up for media scrum

Also looking forward to the royal visit is veteran photographer Ramon Williams, of Christian media organisation Worldwide Photos.

Mr Williams has photographed the British Royal family for decades on their visits to Sydney, including Prince Charles and the late Princess Diana.

He says it is always ‘pretty hectic’ when the Queen comes to town and is anticipating very tight security measures today.

Does he have advice for onlookers who plan to wait outside the Cathedral for a glimpse of Her Majesty?

“Expect the unexpected,” he says.

Host broadcaster the ABC will broadcast the service live across the nation, as well as onto a large TV screen located in Sydney Square.

Onlookers will be able to observe the Queen and Duke and other official guests arrive and leave the Cathedral.

Members of the public are encouraged to use public transport and arrive early to secure a good vantage point.