Soldiers from the Royal Electrical and Mechanical Engineers (REME) are returning to Royal duties after almost 30 years.
The troops from 4 Armoured Close Support Battalion (4 REME) were on parade at Wellington Barracks, London, to prove they are ready to perform public duties for the Royal Family.
Almost 100 personnel - the full company - were scrutinised for security elements, excellence of bearing, discipline, accuracy of step and orders.
Troops also completed intensive drills delivered by Warrant Officer Class 2 Dianne Miller and ceremonial experts from the Coldstream Guards.
They were declared fit for the role and able to commence their duties as Queen's Guards at Royal residences in London and Windsor.
Lieutenant Emile Ramsay, who has followed the training from beginning to end, said the "dramatic change" in the troops' working day has "required a lot of effort".
"The achievement of passing the fit-for-role inspection cannot be underestimated. The majority of REME soldiers will never have done drill with a rifle before."
Watch: The Changing of the Guard ceremony recently returned to Buckingham Palace for the first time since the pandemic began.
4REME's first Queen's Guard will be at Buckingham Palace on Monday 13 September.
The British Army Band Tidworth, which was also inspected on Thursday, will provide musical support during the 4REME's Changing of the Guard ceremonies.
Major John Vance, who commands the REME Company and will be Captain of The Queen's Guard, said carrying out Royal duties would be "a huge privilege".
"Following intensive training the whole team are now ready and excited to step out in front of the public for this unique task."
Over the next two-and-a-half months, the 93 REME soldiers will be guarding the Tower of London, St James's Palace, Windsor Castle and Buckingham Palace
Lance Corporal Shaun Pimlott, who will carry out his first Guard on 13 September, said: "It is such a different role from my usual job as a metalsmith.
"But it is an absolute honour to represent our corps and Army in this way."
It will be the first time a REME sub-unit has conducted state ceremonial public duties since 1992.