Detained journalist Peter Greste has sent Christmas greetings from his Cairo jail cell, saying he feels strengthened by all that has been achieved so far, despite spending almost a year in prison.

In a letter published the week before the December 29 anniversary of his arrest, Greste says he and colleagues Mohamed Fahmy and Baher Mohamed have highlighted the need for journalism in a healthy democracy.

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“The best journalism puts a frame around an issue. It helps define it, clarifies it, makes sense of it. And, above all, it challenges authority,” Greste said.

The Al Jazeera journalists are serving a mixture of seven and 10 year prison terms for broadcasting false news and aiding a “terrorist organisation”.

The Australian thanked his family members and those of his colleagues, as well as their supporters, who have created a “huge global awareness”.

“As we approach the end of our first year in prison, I cannot help but feel proud and strengthened by all that has been achieved so far,” Greste said.

“We haven’t won this fight yet – we are still behind bars after all – but we have made our cause abundantly and unequivocally clear.”

“And for that reason, it really is a very good Christmas.”

“So, from our cell in Cairo, all the very best in season’s greetings.”