I found this Table; an extract from The British Medical Journal, which seems to suggest the first patient to receive a Parks’ Pouch was on the 9 July 1976.
The link below opens as a PDF and the Table is shown at the top of page 3
It appears to be the original Case Study which was first published in The British Medical Journal on the 8 July 1978.
https://www.bmj.com/content/bmj/2/6130/85.full.pdf
Proctocolectomy without ileostomy for ulcerative colitis A G PARKS, R J NICHOLLS
Although, this isn’t the article I found years ago.