Production crews moved on to the site earlier this week and have been seen emptying trucks of equipment.
It is believed the filming is for an explosive storyline of Holby City, which will be screened over the festive period.
Plot lines are still under wraps and the main actors were due to arrive today.
Filming is expected to take up to 10 days on a closed set and, although the prison is shut for tours and events, the new children’s fun house will remain open.
It is not the first time the prison has been used by TV crews.
The interior of the former jail were used in Sky’s production of Lucky Man, starring Cold Feet’s James Nesbitt and Yvette Fielding brought her Most Haunted crew along for a paranormal experience.
The filming coincides with the announcement that the prison has been given a reprieve and continue to run as a tourist attraction until 2019.
Planning permission has been granted to turn the Grade II listed property in to student and private accommodation, a gym, cafe and walled garden but developers have told the bosses of Jailhouse Tours that they will be able to stay on site for all of next year.
Jailhouse Tours runs a number of history and heritage led tours, Aislin’s Funhouse and Immersive Events at the Dana.
And there are a range of events coming up, starting with ‘Shrewsbury Prison Scream Park’, the Halloween scare event running throughout October, Christmas events including a murder mystery dinner and the return of ‘Twisted Fairy-tales’.
There is a full calendar of events planned for 2018 including, Prison Escape, Porridge at HMP Shrewsbury, heritage tours, history days, outdoor cinema, scare events, cell escapes, iCombat laser games and battle archery.
Joel Campbell, CEO of The Campbell Group of Companies, owner of Jailhouse Tours said: “My team and I are very excited about 2018, the events and tours we have planned are going to cement the prison as one of the main tourism attractions.”