I was a bit late to the party with this, which I can now acknowledge as one of the best ever police dramas on British TV. I don’t know how the first few series passed me by and it was really only when the fourth series starring Thandie Newton started gripping the viewers of “Gogglebox” and picking up awards that I realised I had missed out on something special. Thanks to Netflix which has had all the series available to view I have caught up, bingeing on episodes (unusual for me) because I couldn’t wait to find out what had happened.

I’m glad I watched this first episode of Series 5 before Friday’s “Gogglebox” as this was heavily featured with the sofa-sitters open-mouthed at the twists, even on occasions when even I’d rumbled what was going on, they were shouting at their TVs in amazement at the proceedings.

Since the last series which first aired in March 2017 writer Jed Mercurio’s profile has really ascended due to his gripping of the nation over 6 successive weeks in the late summer with “Bodyguard”, a huge ratings hit, but this is very much his bread and butter work, a less showy, superbly plotted and scripted tense hour which is a great antidote to the general cosy feel of Sunday night TV.

Its main quality is its sheer unpredictability which over the five series has seen astounding plot developments no-one could possibly see coming, major characters bumped off and the best scripted police interviews ever. AC-12 is the department set out to investigate police corruption and its three leading lights prove a tight ensemble which is another hallmark of the show.

Neither Vicky McLure as Kate nor Martin Compston as Steve are especially familiar to viewers in other roles and so fit in perfectly as the young guns in the AC-12 department overseen by Adrian Dunbar as Hastings.  Compston is particularly excellent as the tenacious but increasingly world-weary Steve whose position in the Department we’ve invested in since the very beginning.

The opening twenty minutes or so are always essential in a Mercurio plot (remember the bomb  on the train in “Bodyguard”?).  It’s often a big set piece out from which ramifications continue to rumble for the whole series.  Here there is a hijacking of a lorry stuffed with drugs under police guard and one of the perpetrator’s actions towards an injured officer causes questions to be asked.  There is a leak somewhere and AC-12 are out to plug it.

Plot threads from previous series are picked up efficiently.  Member of the team and series regular Maneet was seen in a couple of compromising situations in the last series before taking early maternity leave.  Now back at work suspicions have not gone away with astounding consequences.  Almost everyone would have been caught out by at least one of the three or four major twists in this opener and it is this which is likely to keep the 7.8 million (making it the most watched TV show of the year so far and registering its highest ever viewing figures) who tuned in for the first episode on the edge of our seats on a Sunday night to find out what this superior television event has in store for us.

Line of Duty Series 5 is shown on BBC1 on Sunday evenings at 9.00pm. The first episode was transmitted on 31st March and is currently available on the BBC I-Player.