Xaus led the way despite the rain at Brands Hatch

The Ducati Fila rider made light of an afternoon downpour to record a time of one minute 36.441 seconds.

Xaus, currently in second place in the world championship standings behind team-mate Neil Hodgson, had edged in front of Britain's Chris Walker of HM Plant Ducati on the last lap of the session with Regis Laconi qualifying third.

"This is going to be a very special weekend for me," said Walker.

"It was this time last year HM Plant Ducati asked me to ride for them in 2003 and I really want to repay the faith they've shown in me with a big result or two on our home turf.

From a rider's point of view the racing is as tough as it's ever been Chris Walker

"It hasn't been the easiest of seasons for me so far because of the injuries I've picked up along the way.

"But hopefully that's all behind me now and I should have a fair crack of the whip at Brands.

"There's any number of riders who could be in with a shot to win this weekend and because this is the UK, there's always the threat of the wildcards.

"People have said World Superbikes is a little bit lacking this year but I can tell you that from a rider's point of view it's as tough as it's ever been."

Leon Haslam, riding the Renegade Ducati, was fourth fastest while fellow wildcard entrant Seam Emmett of ETI Racing was fifth and Rizla Suzuki's John Reynolds sixth.

James Toseland of Sheffield, who stands third in the overall rankings, was seventh with Michael Rutter eighth and British Superbike Championship leader Shane Byrne ninth.

World championship leader Hodgson - a notoriously slow qualifier - went 13th fastest while Nick Medd was home in 21st.

The Foggy Petronas riders endured another difficult with Troy Corser 17th fastest and James Haydon in 19th.

1st qualifying session:
1 Ruben Xaus (Spa) Ducati 1:36.441
2 Chris Walker (Gbr) Plant 1:36.575
3 Regis Laconi (Fra) Ducati 1:36.598
4 Leon Haslam (Gbr) Ducati 1:37.482
5 Sean Emmett (Gbr) Ducati 1:37.756
6 John Reynolds (Gbr) Suzuki 1:37.783
7 James Toseland (Gbr) Ducati 1:37.825
8 Michael Rutter (Gbr) Ducati 1:37.830
9 Shane Byrne (Gbr) Ducati 1:37.984
10 Pierfrancesco Chili (Ita) Ducati 1:38.722
11 Gregorio Lavilla (Spa) Suzuki 1:39.512
12 Yukio Kagayama (Jpn) Suzuki 1:39.521
13 Neil Hodgson (Gbr) Ducati 1:39.535
14 Sergio Fuertes (Spa) Suzuki 1:39.638, 15 Dean Ellison (Gbr) Ducati 1:39.768
16 Mauro Sanchini (Ita) Kawasaki 1:40.245