Brunel on Parade received its first public airing at a reception in London.
This was given not by Brunel University or Bristol's Brunel College of Arts and Technology in London but by the Science, Engineering and Technologies Alliance (Semta) which this month becomes the sector skills council for science, engineering and manufacturing technologies.
The inspiration for Sir Patrick's composition is Isambard Kingdom Brunel, who was born 197 years ago this month. Sir Patrick, 80, has long been a favourite of Semta's and Brunel's birthday is celebrated each year with a reception in the Great Hall of the Institution of Civil Engineers in Westminster.
Sir Patrick's new piece was premiered at this year's bash by a brass ensemble, the Wheelwrights'Quartet. The event was attended by some 200 MPs, most of whom appeared to be talking at once. For them, perhaps, the finer points of the music were eclipsed by the greater pleasure of the sound of their own voices. "I'm not surprised," the composer shrugs, philosophically.
Sir Patrick's piece may yet be issued on CD for the wider public to savour.
It is reminiscent of a rousing, RAF-style march-past - but then between 1940 and 1945 Sir Patrick served as a navigator with Bomber Command, flying on raids in Hampdens, Wellingtons and Whitleys.
He says he was approached by a fellow West Sussex resident Michael Wilding, a 79-year-old clockmaker who doubles as leader of the Wheelwrights'
Mr Wilding is a friend of Semta's chief executive Michael Sanderson, who had asked the saxman of the band to play at the Brunel birthday party, perhaps bringing along some new music.
Sir Patrick says: "Semta and the Wheelwrights wanted a march-type thing, so I looked around to see if I had any that hadn't been used, and I had this one."
He donated the hitherto untitled number. He did not write Semta a new piece, he explains, because he is no longer able to.
"It was a march that I had written some time ago, for no particular reason.
The theme had come into my head while I was out walking at Selsey. When I tried it out on the piano it worked, which is the way I work as a composer, or rather used to work.
"Unfortunately old wartime injuries have caught up with me, so I can no longer play the piano."
It also meant that, much as Sir Patrick would have liked to jam with the Wheelwrights, he had to sit out the Semta session.
Sir Patrick used to lay down a mean xylophone - he once appeared on the bill of a Royal Command Performance.
He regards musical composition as a gift. "No credit to me," he says, adding: "Don't get me wrong, no credit to me at all - but I've got perfect pitch and perfect timing.
"If I heard something, I could play it. I never had a music lesson in my life and have no idea of theory."