Armed Forces charity bosses believe the full impact of the Afghanistan conflict is "yet to be seen" as the Queen, the Duke of Edinburgh and senior members of the Royal Family prepare for a service of commemoration at St Paul's Cathedral.
The Prince of Wales and the Duchess of Cornwall, the Duke of Cambridge, his heavily-pregnant wife Kate, and Prince Harry - who served two tours during the conflict - will also attend tomorrow's ceremony, held to mark the end of combat operations in the country, honour veterans of the campaign and remember the servicemen and women who lost their lives.
The families of some of those killed will also take part in the commemorations and v eterans of the 13-year campaign will march past the cathedral in a parade.
Prime Minister David Cameron, Deputy Prime Minister Nick Clegg and Defence Secretary Michael Fallon will also attend with the Earl and Countess of Wessex and the Duke of Gloucester.
But David Muray, chief executive of SSAFA, the Armed Forces charity, says the nature of the issues that those who served in the 13-year conflict are dealing with will take time to deal with.
He said: "Experience tells us that the full impact of Afghanistan is yet to be seen. The very nature of the issues those who served in Afghanistan are dealing with will take some time to unravel.
"SSAFA is already supporting many of those who fought in Afghanistan and their families. The charity is guiding bereaved families through the grieving process, aiding those whose worlds have been turned upside down by life-altering injuries and reaching out to those suffering with the mental effects of war.
"Tomorrow is an opportunity to recognise the courage and sacrifice of the tens of thousands of brave men and women who served in Afghanistan and to honour the 453 servicemen and women who lost their lives fighting for our country.
"As Afghanistan makes the transfer from the front pages to the history books, let us not forget that our Forces have been doing their duty on our behalf, to keep us safe. They have had our backs, now is the time for us to have theirs."
Almost 150,000 UK personnel served in the Afghanistan conflict, and 453 British men and women died in the fight against the Taliban insurgency.
Their sacrifice will be honoured during tomorrow's service, and the Archbishop of Canterbury and the Bishop of London will make addresses of remembrance.
The Archbishop will also bless a cross made of shell casings that adorned a memorial wall in the main Allied base in Afghanistan, Camp Bastion, before it is later moved to the Royal British Legion's National Memorial Arboretum.
Representatives of other nations which took part in the Nato-led International Security Assistance Force will also attend.
After the service there will be a parade through the City of London to Guildhall.
Five detachments will be made up of serving personnel from the Army, the RAF, the Royal Navy and the Royal Marines, with a sixth of up to 400 veterans from the conflict, brought together by the Royal British Legion (RBL).
They will march past St Paul's accompanied by military bands and pipes and drums, with Charles taking the salute.
Aircraft from the campaign, including Chinook, Apache and Sea King helicopters, as well as Hercules transport planes and Tornado attack jets, will roar over the parade in their own salute.
Members of the royal family will later meet those who took part in the commemorations or served in Afghanistan during a series of receptions.
Similar services will also be held at military bases, cathedrals and churches across the country, as well as in Germany for personnel serving there.
A spokesman for the RBL said: "The end of combat operations in Afghanistan provides us the opportunity to reflect on the 453 service personnel who lost their lives in that conflict and the many thousands more who served their country under trying conditions.
"The Legion salutes them and stands ready to preserve their memory and their welfare."
Following the announcement of the service last month, Mr Fallon said he hoped people throughout the UK would join together in "remembering those we have lost and recognising the extraordinary courage and dedication of all those who served".
He said: "They leave a proud legacy - terrorists have been prevented from using Afghanistan as a safe haven for attacks on our streets and it is a safer and more prosperous country."
The final chapter in the 13-year conflict came in October last year when the last British troops were airlifted from the sprawling Camp Bastion base in Helmand Province, leaving just a few hundred personnel in advisory, logistical and support roles to help the Afghan army.