Matt Prior posted the first century of the new LV County Championship season to help Sussex take a firm grip of their Division One encounter with Middlesex on day three at Hove.

England wicketkeeper Prior, who was omitted for the final two Ashes Tests over the winter, survived three drop catches on his way to 125 as Sussex made a first-innings total of 386 in reply to their opponents' 105 all out.

The 32-year-old was finally dismissed by Steven Finn, who did his own hopes of England redemption no harm after his own disappointing Ashes campaign.

Finn was sent home early from the tour in Australia after not getting any game time during the 5-0 Test series defeat and then being declared ''unselectable'' by limited overs coach Ashley Giles.

The right-armer showed any ill-effects of his difficult time Down Under could be behind him as he returned 6-80, although overall it was a frustrating day for Middlesex.

The visitors finished the day on 57-1 - England opener-in-waiting Sam Robson the man out - and 224 runs behind.

Sussex began proceedings on 86 for three and with Prior at the crease on 32.

He had been dropped on his way to reaching that mark on Sunday - day two was then completely washed out - and he had some further luck as he progressed from there, first with Adam Rossington failing to hold on to his drive off James Harris' bowling.

Five overs later, it looked as if Prior might be caught on 55 as he hooked Toby Roland-Jones, but the shot in fact earned a six - the only one of the knock, which would also eventually include 19 fours - as Harris spilled it over the boundary.

Sussex then lost their first wicket of the day with 148 on the board as Finn saw off Matt Machan for 38.

Finn quickly added the scalp of Ashar Zaidi (four) with only four more runs having been added, but Prior was still going strong and reached his 100 just before lunch, which Sussex went into on 209 for five.

The home side had got to 244 by the time Ben Brown, having contributed 44, became the next to fall to Finn, who soon after sent Prior on his way via a catch from Harris.

Steffan Piolet (25) and James Anyon (50) - Finn's other two wickets - as well as Jon Lewis (35) and Steve Magoffin (19 not out) then helped drive Sussex on to their final tally.

After Middlesex's second innings got under way, Robson was bowled for one by Magoffin, but captain Chris Rogers (27) and Dawid Malan (21) saw the away side through to the close.