The thriller, starring Tom Bateman as Dr. Jekyll's grandson and Grant as a spy, horrified many viewers who saw the show at 6.30pm (local time) on Sunday night (25Oct15) due to violent scenes including a brutal murder.

U.K. watchdog The Office of Communications (Ofcom) received 459 complaints, while around 200 more viewers contacted the show's broadcaster ITV to express their anger, bringing the total to more than 800.

Ofcom officials have now launched a probe to determine whether ITV chiefs broke broadcasting rules by airing the show before the U.K. TV watershed, which ensures material unsuitable for children is not broadcast until after 9pm.

"Ofcom has carefully assessed a number of complaints about Jekyll and Hyde on ITV," an Ofcom spokesperson tells WENN. "We are opening an investigation into whether the programme complied with our rules on appropriate scheduling and violent content before the watershed."

After the initial complaints, ITV bosses declared they would not to bow to pressure to change the air time of the programme.

"We issued a warning before the transmission of Jekyll and Hyde advising the parents of younger children they may find some scenes scary," a spokesperson for the broadcaster said.

The statement was made prior to the announcement of the Ofcom investigation.