Labrador Reqs, 12, is the 42nd recipient of the PDSA Order of Merit, which recognises animals that have shown "outstanding devotion to their owner or wider society".

Reqs began his career in 2012, attending more than 500 fires and helping with high-profile investigations before his recent retirement.

He joined the Hertfordshire Fire and Rescue Service after specialist training. There he was paired with his handler, watch commander Nikki Harvey.

She was at the ceremony where Reqs received his medal, and said she was "immensely proud".

"It just sums up magnificently all the work that he's done over the years and we're just extremely proud of that."

Ms Harvey said she quickly formed a bond with Reqs and now they are "the best of friends".

She said that even though Reqs is retired, he still "loves" his tennis ball, as well as food, including a cup of tea.

Speaking about training a fire investigation dog, she said it is all "based on a reward", in the form of the animal's "favourite toy".

"In Reqs's case, that's a tennis ball, so the initial search he is doing is for a tennis ball and then we build that up over a course of searches (so) he is identifying ignitable liquids," she added.

"Then once he identifies the ignitable liquids, he then gets a tennis ball as a reward.

"We're looking for dogs that have got a high search drive, they really want to play with their toy and interact with the toy, and not only just be given a toy to play with - which is obviously their ultimate reward for working - they want that drive to be able to search and hunt for it in effect."

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PDSA director-general Jan McLoughlin said Reqs's "exceptional skills go above and beyond that of normal companionship, making him a very worthy recipient of the award".

"His outstanding devotion to duty and service to society has been demonstrated time and time again throughout his long career," she said.