Series 4 marked the first of the 30 minute twice weekly episodes in place of the 50 minute "originals". The show also lost two of its best characters in Inspector Kite and DI Galloway. Replacements included Inspector Christine Fraser, and PC Pete Ramsey, a slimey ex-DC from Barton Street superbly played by Nick Redding. The series also marks the full time debut of Frank Burnside as Sun Hill's new D.I. - his previous portayal as a cockney wide boy being explained by a backstory involving Operation Countryman. Old favourites still with the show include Sergeants Cryer, Penny & Peters, DS Roach & DC Dashwood, and all the uniformed officers - "Taffy" Edwards, Reg Hollis and June Ackland amongst others.
The main consequence of the move to the 30 minutes/ twice a week format is loss of overall quality. However, when the show is good, it's very good. Fears that the gritty tone of the show would be fatally compromised are only slightly realised - an episode such as "Here We Go With The Loopy Loo" would never have made it to screen as an "original". However, there's still some fairly meaty storylines to be had, most notably Tom Penny's attempts to deal with the aftermath of his shooting in Season 3, as well as epsiodes such as "Home Sweet Home" & "Hold Fire".
Overall, although not as good as the "originals", when compared to the childrens program that airs under The Bill moniker today, Season 4 is a must to see what real policing was/ is all about