Cafe hostage tells of dramatic escape

One of the first hostages to escape the Sydney cafe siege has spoken of the overwhelming relief he felt when he rounded the corner and saw armed police waiting for him.

John O'Brien has described how an ordinary day was thrown into chaos when, along with 16 others, he was caught in an act of terror as self-described cleric Man Haron Monis seized control of the Lindt cafe.

The 83-year-old was able to flee the Martin Place cafe about 4pm on Monday along with two other hostages, barrister Stefan Balafoutis and Lindt worker Paolo Vassallo, about six hours after their ordeal began when they noticed a green button next to the door.

"I have never felt so much relief as when I turned that corner and saw the armed police waiting for me," Mr O'Brien told the ABC.

"All I was doing on that Monday morning was going down for a quick coffee at the Lindt coffee shop after having gone to the eye doctor to have an eye check-up."

He paid tribute to the two hostages who lost their lives when the siege came to a fatal end.

"First I would like to pay tribute to Katrina Dawson and Tori Johnson and offer my heartfelt condolences to their friends and families," Mr O'Brien said.

"My thoughts and prayers are also with my fellow hostages and everyone affected by this terrible event as we all try to come to terms with it."

Dawson, 38, and Johnson, 34, were the hostages who died when the siege ended after 2am on Tuesday.

Monis was also killed when police stormed the building after hearing shots from inside.

Mr O'Brien also thanked the police and emergency services for their actions during the drama.