Grace: why tonight's episode confirmed Brighton-based detective series as essential viewing

But, at last, it is happening again – with Grace and Brighton proving the best crime double act in more than a generation.

The first TV adaptation of the first of bestselling author Peter James’ Brighton-based Roy Grace detective novels impressed on its debut last year.

But with the second episode last week, there was a huge sense that the whole thing stepped up a gear. The actors actually started to become those characters that we have been reading about across 17 brilliant novels so far; and importantly, we also started to get a genuine sense too of the relationships between them.

Tonight, the Grace series, with its third episode, took maybe its biggest leap so far: the one that fully establishes it as a thrilling series which is now fully into in its stride – a series with the legs to run and run for as long as Peter James is prepared to keep writing the novels.

Did you catch Peter James’ cameo?

And thank goodness, there is no sign of him slowing down. Novel number 18 comes out in the autumn; and episodes four and five will be broadcast next Sunday and the Sunday after. All we have to do is get through this week. The series is now absolutely required Sunday night viewing.

Tonight’s episode was Not Dead Enough, a TV dramatisation of James’ third novel in the series. And it offered a first rate mystery. A body washes up on Brighton beach as Grace jogs by; before long there’s another body, the wife of a wealthy Brighton socialite – and there are reasons to believe he’s the killer.

Except… and this is Peter James’ brilliance… the socialite was most definitely somewhere else.

How can one person be in two places at exactly the same time? That’s the mystery that Roy Grace has got to unravel.

Grace - how John Simm is conquering the TV screen as Peter James’ Brighton detective Roy Grace

But the real significance in this episode is undoubtedly the introduction of pathologist Cleo Morey. Zoe Tapper in the part instantly brings alive the connection which sparks between her and Grace.

There have been chunterings that Grace in episodes one and two was pretty morose: straightaway we start to see a different side to him.

Simm makes the detective light up in Cleo’s presence; and Tapper as Cleo makes us see why.

And instantly the stakes are higher.

In the penultimate scene, post the big revelation, we see huge compassion in Grace’s words to a key figure in the mystery. Meanwhile, we are wondering, while probably knowing, what’s going to come of Grace and Cleo as an item? Further depth comes from Grace’s close mate Branson – and his words at the end.

It all adds up to the perfect platform. The countdown starts now for episodes four and five in a series which tonight most definitely came completely alive – complex without being convoluted; at the extreme ends of human behaviour but also thoroughly rooted in our humanity.