Middlesex are hoping to stage a Twenty20 Cup quarter-final at the Brit Oval, home of Surrey, their great London rivals, if, as now seems likely, they finish top of the South division because they will not be able to play at Lord's in the week of the first npower Test match against South Africa.

Their young side, including three 19-year-olds, contained Sussex to 151 for seven with one of them, Steven Finn, the England Lions fast-medium bowler, taking three for 22 in his four overs.

Another, Billy Godleman, then struck 69 off 49 balls, including two sixes and seven fours, to put them on the way to their seventh win in nine matches, which was completed with an over to spare.

Sussex, who had no hope of reaching the quarter-finals after winning only two of their first eight games, rested Chris Adams, the captain, and Robin Martin-Jenkins, their hard-working all-rounder, with a view to their important LV County Championship match against Lancashire that starts at Hove on Sunday.

Matthew Prior, again playing as a specialist batsman with Andrew Hodd keeping wicket, took over the captaincy and provided the only real fireworks for a crowd that was understandably subdued after their side's thrashing at Chelmsford the night before.

Prior hit 30 off 17 balls including two sixes and three fours before driving David Burton, 22, a fast-medium bowler from Dulwich who was making his Middlesex debut, to long-on but Michael Yardy needed 41 balls for his 43 with only four fours.

Murray Goodwin and Dwayne Smith never got going, Rory Hamilton-Brown was run out without facing a ball and Sussex needed a late flourish from Carl Hopkinson and Will Beer, who took 32 off the last three overs, to achieve a measure of respectability.

Middlesex's third 19-year-old, Dan Housego, a batsman who has played for Berkshire in the Minor Counties, opened with Godleman and contributed 17 to a partnership of 65 in eight overs before he was caught behind down the leg side off James Kirtley.

Middlesex stumbled for a couple of overs after Godleman was brilliantly caught by Hopkinson on the long-off boundary off the leg spin of Will Beer, yet another 19-year-old, and Eoin Morgan was bowled first ball by Yardy on the day he signed a new, three-year contract, but Ed Joyce and Dawid Malan calmly accumulated 43 from five overs to make victory a formality.

Sussex

M H Yardy c Henderson b Finn 43
M W Goodwin b Murtagh 8
*M J Prior c Finn b Burton 30
D R Smith c Henderson b Finn 9
R J Hamilton-Brown run out 0
C D Nash c Henderson b Finn 12
C D Hopkinson not out 26
A J Hodd lbw b Henderson 5
W A T Beer not out 17
Extras (w 1) 1
Total (7 wkts, 20 overs) 151

C J Liddle and R J Kirtley did not bat.

Fall of wickets: 1-25, 2-70, 3-85, 4-86, 5-103, 6-104, 7-119.

Bowling: Finn 4-0-22-3; Murtagh 4-0-44-1; Henderson 4-0-22-1; Burton 2-0-17-1; Udal 4-0-39-0; Malan 2-0-7-0.

Middlesex

B A Godleman c Hopkinson b Beer 69
D M Housego c Hodd b Kirtley 17
T Henderson b Beer 17
*E C Joyce not out 28
E J G Morgan b Yardy 0
D J Malan not out 15
Extras (w 3, nb 4) 7
Total (4 wkts, 19 overs) 153

S D Udal, T J Murtagh, B J M Scott, D A Burton and S T Finn did not bat.

Fall of wickets: 1-65, 2-101, 3-110, 4-114.

Bowling: Smith 4-0-25-0; Liddle 4-0-42-0; Kirtley 3-0-29-1; Yardy 4-0-25-1; Beer 4-0-32-2.

Umpires: N G Cowley and R K Illingworth.