Antiques Roadshow expert John Foster told a guest his model is worth a mint - but was left stunned when he heard why he just couldn't sell it.
The man brought in a rare Donald Campbell Bluebird, and was informed that it was worth a huge amount.
The item was valued at up to £8,000 but the collector said he would never part with it because it just means too much to the family.
The impressive model belonged to the man's grandfather - and it would just be too difficult to cash in on.
Viewers watching Sunday's show were impressed by his need to keep hold of it.
He told John: "My grandfather took over lead constructor with a company in Coventry that went on to the land speed record in 1964.
"I think it was either made for design presentation or for even aerodynamics for a wind tunnel perhaps.”
The expert said: "What part of the element of the story that I find amazing on this, is they broke the land speed record at Lake Eyre in 1964.
"They achieved I think it was 403mph. They were all disappointed when they achieved that because this was capable of 500mph or just under 500mph.
“There was bad weather, there were all sorts of issues going on. So, to be disappointed only to get 400mph!”
He then told the man: "An auction estimate, it’s tricky but somewhere between sort of £5,000 and £8,000.”
But the guest shocked everyone with his response.
Immediately promising he would be keeping it, he explained to John that flogging the Donald Campbell Bluebird model was just something he just couldn't do.
"Wow," he replied after hearing what it could fetch.
"But I'm not in the habit of selling, but it's great - thank you.”
