The evensong at Westminster Abbey in London marked seven decades since the battle in North Africa, which was widely hailed as the turning point in the Second World War.
Around 40 British and Australian veterans, many of whom are now in their 90s, were part of a 500-strong congregation to honour those who fought in the 14-day battle.
More than 4,000 Allied servicemen lost their lives and almost 9,000 were wounded in the combat that saw General Sir Bernard Montgomery's troops defeat German general Erwin Rommel's Afrika Korps.
Addressing the congregation, Chief of the General Staff Sir David Richards said: "The Battle of El Alamein was a turning point in the Allied fortunes in the Second World War, a victory that Churchill referred to as a bright gleam that caught the helmets of the soldiers, and cheered all our hearts.
"Men from all three services played their part, not least those from my own regiment, the Royal Artillery. I am very proud to be here today, paying tribute to them, and their example of courage and professionalism which today's armed forces constantly strive to live up to."
Veteran Robert Lay, 91, from Northumberland, described the service as a "timely opportunity" to remember those who fought in the battle.
Mr Lay, who served with the 5th Armoured Tank Regiment at El Alamein, said: "The 70th anniversary of the Battle of El Alamein is for me a timely opportunity for remembrance of all my close friends and associates, particularly my first tank crew - closer than brothers - who I travelled with almost all the way to Tunis. All of them I believe were killed by the time we crossed the Seine in 1944."
During the service, two wreaths were laid at the Grave of the Unknown Warrior. The first was by the Chief of the Defence Staff on behalf of The Duchess of Cornwall, whose father Major Bruce Shand served with the 12th Lancers at El Alamein. A second wreath was laid by the Chief of the General Staff on behalf of the armed forces.
Under the command of General Montgomery, nearly 200,000 British, Australian, New Zealand, South African, British Indian, Free French and Greek Forces defeated the Axis powers.
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