Outside teams of police in blue boiler suits walked around the cathedral precincts making last-minute checks.

Security for the funeral service of Curtis Cheng, the civilian police accountant shot dead by 15-year-old Farhad Jabar outside the NSW police headquarters in Parramatta two weeks ago, was always going to be tight.

Alongside the funeral bouquets was Mr Cheng's Police Diligent and Ethical Service Medal presented to employees upon completion of 10 years of service.

A police spokeswoman said that he was also today to be posthumously awarded the Commissioner's Commendation for Service medal.

Police commissioners or their deputies from all states in Australia were to be represented and in total some 600 police officers were expected to attend.  NSW Police Commissioner Andrew Scipione was to read the Service Valedictory which at the conclusion of his address he was to present to the Cheng family.

Mr Cheng's widow Selina and her two children, son Alpha Cheng and daughter Zilvia Cheng were the lead mourners.

A steady queue of those wishing to pay their respects formed at the main cathedral entrance and a small group of Chinese quietly sang close by the main steps.  Armed officers remained posted throughout the precincts.

Mr Cheng followed the Buddhist religion and one of the readings during the hour-long service was to be given by a Buddhist monk.

Also attending were Premier Mike Baird, opposition leader Luke Foley and Police Minister Troy Grant as well as Governor of NSW General David Hurley.

The welcome was made by Catholic Archbishop of Sydney Anthony Fisher but the service was to be led by  Fr Paul O'Donoghue, Senior State NSW Police Force Catholic Chaplain.

Mr Cheng's daughter was to give a reading from the book of Wisdom. It began: 'The virtuous man, though he die before his time, will find rest.' A eulogy was delivered by Mr Cheng's son.

At the end of the service police including the commissioner were expected to form an executive guard of honour at the main entrance to the cathedral with officers lining College Street as the procession departs.

Although the public was invited to attend the family asked that their privacy be respected.

But the family did give a poignant message at the back of the order of service booklet opposite the now familiar portrait of the family.

It said: 'The Cheng family wishes to convey our sincere gratitude to all those present at this memorial service for Curtis. He will be missed by all of us. We will cherish our memory of him forever. In this time of sorrow, we have been heartened by the innumerable expressions of condolence and support from those who are close to us, leaders in the community and caring people from all walks of life. We truly believe that the outpouring of support is a reflection of a harmonious and thriving multi faith and multicultural Australia.'