The day that Phil crossed the great divide!
Some 43 years on Chisnall remains the last player to be transferred directly between the two clubs.
The bitter rivalry that developed over the following decades made the idea of doing business unpalatable for both sets of fans.
But Alex Ferguson was less than over-joyed at the prospect of one of his players joining their arch rivals.
It's all a far cry from the circumstances surrounding Chisnall's move to Anfield.
"I've become the answer to a quiz question in recent years," admitted the 64-year-old.
"It was unusual to go from United to Liverpool back then, but there wasn't a big deal made of it.
"Liverpool had only been in the First Division for two years before they won the league in 1964.
"They were only just establishing themselves in the top division and the rivalry between United and Liverpool fans wasn't as strong then as it is now.
Liverpool's real rivals were Everton, while United's were Man City.
"I played for England Under-23s against Germany at Anfield and we won 4-2. I'm not sure whether Shankly was there but it was just before Liverpool came in for me.
"United finished second in '64 and I remember Matt Busby Sir Alexander Matthew Busby, CBE  (born 26 May 1909 - died 20 January 1994) was a Scottish football player and manager, most noted for managing Manchester United between 1945-1969 and again for the 1970-1971 season.
"I was 21, Liverpool had won the league and were a great club. Liverpool was a vibrant place with the Beatles making it big and Shankly reviving Liverpool FC, so I decided to go for it.
"After I signed I went back and played for Liverpool against United at Old Trafford Old Trafford commonly refers to two sporting arenas:
. I can't remember getting any stick - it wasn't like that back then."
Chisnall had scored 10 goals in 47 games for United but he struggled to make the grade at Anfield.
In three years he made just eight appearances but he did have the honour of making his league debut against Arsenal at Anfield, which featured on the first edition of BBC's Match of the Day, and he also played in the Reds' first European tie against KR Reykjavik in Iceland.
He was sold to Southend for pounds 12,000 in 1967 but insists he never rued the moment he quit United.
"Things didn't really work out for me but I didn't regret joining Liverpool," he said. "It was just circumstance really - I didn't hit it off.
"It was a great side with players like Ian St John, Ian Callaghan Ian Robert Callaghan (born 10 April, 1942 in Toxteth, Liverpool) is a former footballer who holds the record for the most appearances for Liverpool. Life and playing career
..... Click the link for more information., Peter Thompson, Roger Hunt, Willie Stevenson, Gordon Milne and Tommy Smith so it was always going to be tough to get into the side.
"In the space of a year I played under Matt Busby, Bill Shankly and Alf Ramsey, who was manager of England Under-23s at the time. The three of them were all great managers and it was a privilege to play for them.
"These days I live close to Old Trafford in Urmston and I like to see both United and Liverpool do well.
"I really don't favour one of them above the other. Both clubs have had spells when they have dominated and these things come full circle. I'm sure Liverpool will come back strong."
Chisnall, who ran a betting shop business after hanging up his boots, suffered a heart attack two and a half years ago but is now in good health.
And he is keeping a close eye on whether Argentine left-back Heinze follows in his footsteps.
He said: "Heinze is a very good player and I can understand why Liverpool would want him.
"You wouldn't think United would sell him to them because of the rivalry, but Alex Ferguson is his own man and you can't guess what he's going to do.
"Some people said it was a big mistake selling Van Nistelrooy to Real Madrid but there was no backlash from that.
"Ferguson keeps having success and people trust his judgement.
"It's much more difficult for players to move between rival clubs now because football is like a religion these days.
"Back when I played, you enjoyed it and if you lost to a good side you accepted defeat. The game wasn't as intense in those days and there wasn't that mentality of win at all costs."
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