Happy Choppers is a Banksy series that depicts military helicopters adorned with pink bows.
The Holywell Row take was considered a security risk by the owner of the office building it was left on, who had it painted over before selling the building “without mention of its existence”.
The anonymous vendor said he learned of the artwork by chance after purchasing the building.
He said: “We were astounded to discover that our newly purchased office building was the canvas for an artwork of this significance.
“Banksy is a real icon of our time, his art is so important to preserve for future generations.”
The Happy Choppers piece, which was removed from the wall in sections and preserved, is expected to sell for between £500,000 and £800,000 when it is auctioned this week.
