Each year, tens of thousands of little remembrance crosses are planted in the grounds surrounding the Abbey, each one with a dedication written to a loved one or friend killed in battle.
This year, there will also be a plot of crosses to remember those men and women who died in Iraq and Afghanistan. Each one will bear a name, photograph and dedicated message.
Joining Prince Philip were Anna Aston and her seven-year-old daughter, Pagan, and Amanda Binnie; both women lost their husbands in Iraq and Afghanistan, respectively.
Their crosses will be a personal tribute to Corporal Russell Aston, who was in the Royal Military Police and was killed in Iraq in June 2003, aged 30, and Acting Sergeant Sean Binnie of The Black Watch, 3rd Battalion The Royal Regiment of Scotland, who died in a fire fight with insurgents in Helmand province in May 2009, aged 22.
This year's Royal British Legion Poppy Appeal targets support for the wounded and bereaved of Afghanistan, with a sobering poster campaign featuring a young war widow and a double amputee, who is still serving in the Royal Marines.
Visiting the Field of Remembrance today was Mr John Lucas who served in the RAF Regiment between 1951 and 1955. Keen to keep the memory of his comrades in the public's mind he said:
"I come every year. I know the wartime generation is dwindling now, but the RAF goes on serving in all sorts of conflicts around the world. I like to remember my friends and I want others to know what they did."
Flight Sergeant Sue Brown teaches at the Royal Centre for Defence Medicine at Selly Oak Hospital in Birmingham and pointed out crosses representing two of her branch's most recent losses to a helicopter accident in Akrotiri.
Another cross, bearing the name 'Corporal M Cook', has special significance for the nursing service.
Flight Sergeant Brown said:
"We now award an annual prize in memory of Corporal Cook to the best nurse in training. I consider it a great honour to be here. Having just returned from Iraq where we lost four lads, I consider occasions like this to be very important."
Since 2003, the Royal British Legion has provided financial help to over 10,000 Service personnel and recent veterans of Iraq and Afghanistan. The Legion represents one-third of all the appeals for higher compensation payments for injuries suffered in Afghanistan, and its campaigns have led to increased compensation awards which have placed an extra £7.5m in the pockets of the most seriously injured.
The Legion currently spends more than £1m per week in its work helping over 130,000 other members of the Armed Forces family - dependants, veterans and the bereaved. This year it hopes to extend its reach to more than 160,000 beneficiaries.
The Field of Remembrance in the grounds of Westminster Abbey, Parliament Square, London, is open to visitors daily between 0900hrs and 1800hrs from Thursday 5 November until Sunday 15 November 2009.
A second Field of Remembrance is situated behind City Hall in London and is also open to visitors daily between 0900hrs and 1800hrs until Sunday 15 November 2009.