Nottinghamshire 360 and 177 for 1 (Hameed 91, Slater 70*) lead Somerset 470 (Abell 111, Pretorius 95*, Pennington 5-96) by 67 runs

Pretorius, who spent part of last season with Durham, hammered six sixes and eight fours in a 71-ball assault to ensure that the efforts of Tom Abell and Tom Lammonby on day two were not wasted.

Somerset had suffered a mid-innings stumble from 315 for four to 356 for eight and were still in arrears until Pretorius and Jack Leach (37) put on 79 in rapid time, the 29-year-old Pretorius missing out on a second career hundred only because he ran out of partners.

Earlier in the day, Abell could add only six to his unbeaten 105 on Monday before he misread a ball from Harrison that trapped him leg before. A glancing blow on the helmet facing fast bowler Stone had hardly helped his cause.

His dismissal sparked a flurry of wickets. New batter Kasey Aldridge lasted only seven deliveries before being brilliantly caught at second slip by Harrison off Pennington, who found some extra bounce in his next over to frustrate James Rew, caught behind for 49.

At 325 for seven in the 99th over, the sides were level on points, yet the next 11 overs saw Somerset surge ahead thanks largely to Pretorious, whose aggressive hitting brought him a 32-ball half-century.

Pretorius hammered six over midwicket off Pennington and cleared the rope three times off Harrison, who was hit down the ground for another maximum by Leach. Back-to-back fours off Pennington from the England man raised the 400-mark in the 107th over.

Pennington had Overton (20 from 13 balls) leg before and Harrison dismissed Leach via an edge behind soon after lunch, but Nottinghamshire missed out on a third bowling point. Not only that, they were powerless to stem the flow of runs from Pretorious.

He launched one enormous slog-sweep off Harrison that achieved the not inconsiderable feat of clearing the Smith-Cooper Stand before driving Pennington for his sixth six - and could count himself mightily unfortunate to be left stranded when last man Jake Ball, who faced just five balls and contributed not a single run to a 35-run partnership, was leg before to give Pennington his five-for.

Somerset were in a commanding position, in theory at least. Yet they would almost certainly have to bowl Nottinghamshire out for a second time if that position were to become a platform for a win, which looked potentially to be a tall order on an increasingly docile pitch.

Thereafter, little happened to challenge that assessment. Dusty footmarks offered something for Leach to work with bowling from the Radcliffe Road End. The left-arm spinner was in action as early as the eighth over as openers Hameed and Slater set about negotiating the 26 overs up to tea but fashioned only one real chance in that period, the left-hander Slater put down by Overton at slip on 27.

It allowed the pair to reach the interval with 72 runs knocked off the deficit, a platform from which their partnership became the biggest opening stand of the season for Nottinghamshire when it passed 81. Both completed half-centuries soon afterwards, the captain from 101 balls, Slater from 107.

The final session similarly brought no rewards until the last 20 minutes of the day when Overton, bringing himself back for one last burst of pace, with Rew standing up to the stumps, bowled Hameed nine short of a century to break the partnership on 172.