Andrew Morgan, 69, was stunned when he found out one of his ewes had delivered eight lambs - after a scan just two months earlier revealed she was only having four.
Dad-of-two Andrew has been lambing for 50 years and described the ultra-rare birth as 'one in 100 million'.
He said he didn't believe his son in law Philip Hewit, 57, when he called and told him about the amazing delivery at Sunnyside Farm, near Reston, Scottish Borders.
Andrew, who has around 1,000 ewes on the farm, said: "No one knew she was going to have eight, she had only been scanned for four.
"My son in law delivered them and when he called to tell me I didn't believe him, I said no sheep has eight lambs.
"It was a complete shock.
"I think it's a UK record, I have never seen anything like it before in 50 years of lambing and I think it's once in a lifetime, for me anyway.
"The ewe was fine after the birth but very tired after carrying eight lambs for around 145 days."
Sadly, two of the lambs have died since the birth on March 18, after mum, a five-year-old Suffolk cross, lay on top of one, while another was too small to survive.
Grandad-of-three Andrew said they are caring for four of the tiny sheep, feeding them powdered milk by hand, while mum looks after the other two.
He added: "We left three with her to start with but unfortunately she lay on one and it died.
"The others we took to bottle feed with powdered milk but the smallest one didn't make it, which left us with six.
"They were a lot smaller than a lamb would usually be.
"We don't do anything special with the sheep, we didn't use hormones or anything on her to try and produce eight lambs.
"We only really want a ewe to have two as that's the most they can feed at once."
In 2015 a sheep at a farm in Devon was said to have the broken the British record after a ewe gave birth to seven lambs.