Nigel Logan was brewing beer on a small scale to feed his beef cattle on their 140 acre farm near Gracehill in County Antrim.
It made for "happy cows" it tenderised the meat, and as they discovered, it didn't taste at all bad.
"My father loved it, he would take the odd pint down the back along with the cows," said Nigel.
"That was the deciding factor. It was that that made us think it's time we got this into the bottle."
So they made a big decision.
They opted to move from making it with home brew kits, to investing in a lot of expensive stainless steel, and producing it for sale.
It's a diversification scheme with a difference, and William is one of a small number of farms, which has tapped into the growing taste for locally produced beers.
His Hillstown Farm brewery supplies Tesco and a hundred off-licences around Northern Ireland with a range of wheat beer, ales and stouts.
It was a innovative move and one which may prove to be well-timed given the current uncertainty over the future of farm support.
And it coincides with a survey which shows that very few Northern Ireland farms plan to diversify after Brexit.
The results of the NFU Mutual survey found that just 6% of farms here were considering moving into things like renewables or property letting, even though the vast majority of such schemes, turn out to be successful.
The main reasons given for not diversifying were problems in getting finance; lack of interest amongst family members and poor broadband.
The cattle are still benefiting from the farm's stout, its regularly mixed with grain and fed to them.
Nigel says its difficult to strike a balance between the beer and the beef.
He says the focus for now is on the brewing because it's a growing part of the business, but his first love is farming.
The farm income comes roughly 50/50 from the farming and the fermenting.
But Nigel believes that in the years to come the bulk of the business income will come from brewing.