The 3.5ft tall Chinese panels were discovered after the elderly man moved to a care home and his children got valuer Richard Bromwell to take a look around the home.
Mr Bromwell discovered one of the porcelain paintings on a wall, before finding two more in bubble wrap under the bed and another hanging in the landing.
He spoke to various Chinese dealers but, after receiving little interest, gave them a £300 value before sending them to auction.
However, on the day of the sale, the auction room was packed and there were even ten art dealers from overseas on telephone lines.
An intense bidding war eventually led to the four floral panels selling for a hefty £516,000 to an anonymous Chinese buyer who was bidding over the phone.
Mr Bromwell telephoned the widower's children to tell them about the success, and is quoted in the Daily Mail as saying: "I telephoned the client and she had forgotten all about the sale. I told her that I had some good news. Her brother was with her and there was a moment of silence followed by lots of laughter."
The pensioner had inherited the pricy paintings from his dad, who brought the pieces - which depicted the four seasons - home from Hong Kong in the 1960s.
Wow! Try REVEAL Mag for FREE on Android tablets!!! Find out more here
Got an iPad or iPhone? Reveal Mag is specially designed to fit! Find out more here