Denis Parkin joined Granada Television in 1957 as a designer and first worked on the Welsh programme and later editions of Skyport and Knight Errant Limited. In 1960 he worked on Biggles where he first encountered Coronation Street writer and creator Tony Warren. When his new serial, then-titled Florizel Street, went before the cameras for the first time as a two dry runs, Parkin was the designer on the production. He and Warren toured the back streets of Salford looking for a typical terraced street on which to base the design of their fictional counterpart and eventually settled on Archie Street in the Ordsall district (although there were several distinct differences between the real-life street and its eventual television version, such as no pub). Parkin also had to design the inside look of the terraced houses and make each one different in order that the viewers would know which domicile they were watching:
- "The hard part was making them all look different in black and white, so we had long talks about characters. I decided there’d better be a variation in at least one of the houses, so No. 9 was given a sort of glazed lean-to at the back. It was to make a difference. Seven houses in black and white; to make them all look individual was quite a job."
He also told Weekend magazine in May 1961 that:
- "Our biggest problem is getting the sets into the studio. We have to work it out like a huge jigsaw puzzle. I started off with wallpaper in the rooms, but the sets are so small that the designs get confused with the actors' heads on the screen. So we had to strip it all off."
Parkin was the sole designer on the first three years of the programme and in that time designed not just the seven houses, the Corner Shop, the Rovers Return Inn, the Vestry, the Glad Tidings Mission Hall and the shops seen on Rosamund Street, but also many other settings as location filming was an exception rather than the norm in the programme’s early days. Senic designs built inside the studio meant to replicate outdoors also fell to his lot as well and parks and railway stations were therefore part of his remit. Until 1968, the programme had no outside lot and therefore the Street had to be erected inside the studio, complete with cobblestones painted on the floor and Rosamund Street and Viaduct Street accomplished by the use of painted backdrops. He encountered difficulties with the scripts when over-ambitious writers wrote for too many sets within the cramped confines of Studio 2 (later Studio 6) at Granada’s Quay Street studios in Manchester so he volunteered to attend script conferences to make it clear to writers where the physical boundaries of the settings they were contemplating must lie.
In addition, he was called on to supply several illustrations for TV Times showing the geography of the Street and its setting within Weatherfield for viewers. His main illustration appeared in a special four-page pullout for the Christmas 1961 edition of the magazine but he also contributed an illustration for the 1970 1000th Episode TV Times Souvenir which showed how the Street might look in 1980.
Parkin returned to the programme as its credited designer in 1965 for a further stint into 1966 and for further shorts periods in 1968, 1969 and 1970. When in 1968 it was decided to erect the Street set in a railway yard - complete with extant viaduct - that stood on Grape Street behind the Granada Studios, Parkin was assigned to oversee the operation. He was also called back in late 1969 when funds were allocated to rebuild the set on the same site but this time in brick and in 1982 when the entire set was moved and rebuilt to a larger site a couple of hundred yards east on the other side of a bonded warehouse Parkin also oversaw the rebuilding and slight modifications in the design. When the set was officially opened on 5th May 1982 by Her Majesty the Queen, Denis Parkin was one of four production people chosen to meet the VIP visitor along with Tony Warren, Bill Podmore and H.V. Kershaw. This was his last known connection with the programme.
Throughout his Granada career he also worked on many other productions, including all the main Street spin-offs Pardon the Expression, Turn out the Lights, Rest Assured and The Brothers McGregor along with designs on The Verdict is Yours, The Villains, City 68, The War of Darkie Pilbeam (scripted by Warren), Nearest and Dearest, A Family at War, The Life of Riley, The Ghosts of Motley Hall, Leave it to Charlie and the opening episodes of Granada’s attempt to emulate the success of Coronation Street with their 1985 soap Albion Market. He retired from Granada in the late 1980s but his basic design templates for the Street set itself and many of its interiors, especially the bar area of the Rovers, are seen on millions of television screens several times a week to this day.