The Prince of Wales has paid tribute to British forces fighting in Afghanistan in a Christmas radio broadcast to troops serving overseas.
Charles thanked the servicemen and women for their relentless courage and said the nation owed them "an everlasting debt of gratitude".
In his message, recorded last week at St James's Palace and aired this morning, the Prince said all those stationed abroad were very much in his thoughts and prayers.
He added: "I also wanted to pay tribute to the extraordinary contribution made by those of you who belong to our Armed Forces, in all sorts of different parts of the world.
"Nowhere is your fortitude and relentless courage more clearly on display than in Afghanistan, where your resilience, patience and determination to see the job through - usually in impossibly difficult conditions and circumstances - is, quite simply, humbling."
He also joked about receiving a "rare" letter from his younger son, Prince Harry, an Apache helicopter co-pilot gunner serving with the Army Air Corps.
He has been stationed at Camp Bastion since September.
Christmas broadcasts to British troops serving abroad have been made by the Queen in the past. Her last message was recorded in 2006.
Charles's words of support for the servicemen and women were aired on the British Forces Broadcasting Service radio at 11am.
The Prince is Colonel-in-Chief of a number of regiments serving in Afghanistan.
He said he knew about the hardships troops face because of the regular reports from his units - and the occasional contact with Harry.
He said: "I am well aware of the discomfort and privations you all endure with seemingly endless reserves of good humour.
"In addition to the intense heat and dust of the summer and the freezing winters, you face the constant, terrifying threat of IEDs (improvised explosive devices), attacks from rockets, grenades and small arms fire almost every day - and sometimes these attacks come from infiltrators hidden among those who are supposed to be working alongside you as allies.
"And yet you all seem to bounce back in an almost unbelievable way, despite the setbacks and vicious insurgent attacks."
Charles is Colonel-in-Chief of four military units which have troops serving in Afghanistan at the moment - The Royal Dragoon Guards, Army Air Corps, The Royal Gurkha Rifles and The Mercian Regiment.
He added: "With two sons currently serving in the Armed Forces, one of whom is with you all out there, I really do have at least some understanding of what your loved ones on the 'home front' are going through."
He said servicemen and women could keep in touch with relatives through phone calls and the internet "or, in the case of my younger son, to receive a very rare and precious letter in answer to mine".