Lt.-Col. Mark Flint was one of 10 New Brunswickers who represented Canada at Queen Elizabeth II's funeral service on Monday.
He currently commands the North Shore (New Brunswick) Regiment in Bathurst, of which the Queen was Colonel-in- Chief.
Flint said the experience was both a privilege and a challenge.
"It was tremendously detailed planning," Flint told CBC New Brunswick News at 6 on Monday "The British military did an absolutely fantastic job, both in terms of security and orchestration."
He said this was the biggest security operation he's witnessed, with about 10,000 security personnel spread across London.
Flint said he and about 1,800 other soldiers from around the world rehearsed a full dress practice in the middle of the night after he arrived in London at 1:30 a.m. Wednesday.
"We marched that parade route, we went through all of the drills, all of the preparations as if it was the actual procession itself," said Flint.
"It was a little bit eerie being in the middle of the night with no spectators and you're marching down these big streets."
Flint said it was a challenge synchronizing with soldiers from different militaries and learning a new cadence.
But, he felt a sense of honour and privilege marching alongside his counterparts and to be in the presence of the Royal Family during the service at Westminster Abbey.
He said the enormous crowd of spectators remained quiet throughout the parade.
"It was a very sombre moment as we marched the streets and through the arches and all the way up Wellington Gate," said Flint, "It was quite an emotional event."
Procession of honour in Fredericton
In Fredericton, soldiers marched from the Government House to the Christ Church Cathedral on Monday for a commemorative service.
"The whole day will be something you preserve in your memory forever," Premier Blaine Higgs said at the service.
"It shows what convictions Queen Elizabeth II had, her strong faith, the standards that she lived to."
A ceremonial gun salute also took place as part of the service.
Attendance was invitation only, but the event was live streamed for the public.