The respective hosts usually come out on top in this annual contest, although Pavilion won home and away last year.
They took three of the five games on Thursday, May 15 but were undone by a heavy defeat on the slowest rink, losing 22-8.
Horsham, skipped by Lesley Grogan, were 10-1 ahead after six ends against Archie Davis, Chris Cheeseman, Simon Ritter and skip Warwick Davis. Pavilion took only six of the 18 ends, with the two shots they dropped on the last proving important.
Horsham won on aggregate by 81 shots to 79 and will be confident of regaining the trophy when the clubs meet again on August 14.
Their other success came on the captains' rink, where Gerard Donck's four scored a five on the last to win 22-17 against Pat Edmonds, Sonia Burden, Roger Dutton and Pavilion's captain, Richard Krupa. The hosts had led by two with two ends to play before Horsham tied the game on the 17th.
Colin Davey skipped Pavilion's top rink of Ian Down, Sue Gubbins and Peter Tomley, who defeated Debbie Bown's rink 19-9. Nine shots in four ends from the fourth gave the hosts a commanding lead that they defended impressively.
Allan Banks, Pam Duffield, Dave Thomas and skip David Berry produced a strong finish to beat Ric Davey's rink 15-11. Trailing by a couple with five ends to go, Pavilion scored three successive twos, with a single on the last sealing the deal.
Alan Cheeseman skipped Linda Carter, Richard Burden and Bryan Bodicoat to an exciting 20-17 victory against Dave Marden's rink.
Pavilion moved four up after four but trailed by two going to the 17th. They scored the only six of the entire match to seize control and ensure there would be little between the rivals when the second leg is played in three months.
Pavilion Bears lost their second match of the season in the West Sussex League 75-58 at Pulborough, despite winning on one rink and drawing on another.
Jeremy Simpson, John Winkley, Francis Fahey and skip Paul Ward earned two points with a 20-15 victory against Steve Adsett's rink.
The Bears gained an early 6-0 lead, lost it just as quickly and took control on the 13th end with a six that Pulborough couldn't equal.
Mick Steggell, Russ Doherty, Colin Davey and skip Simon Davey drew 17-17 with Malcolm Gray's rink.
The Bears scored a six on the eighth end to move seven shots clear but were caught on the 14th when Pulborough hit back with a five. Three up going to the last, the Bears lost the lead again as Pulborough shared the points.
Dave Thomas, Allan Banks, Tommy Walker and skip Jamie Dunk led John Brown's rink after nine of the 18 ends. Pulborough took six of the remaining ends and won 16-11.
Ian Younger took top rink for Pulborough with a 27-10 victory against Nour Dissem, Ian Slater, Ian Godden and skip Richard Maton, who dropped a six on the second end and a five on the last.
Pavilion's third Brodie Tray match of the season ended in a second win, by 68 shots to 57 against Shoreham, earning six points for the hosts.
They led on all four rinks going to the final end on Saturday, May 17 but the visitors produced a strong finish to turn the tables in two games, thus taking the other four points.
Helen Beale and Jamie Dunk in the pairs registered the hosts' first win, defeating Suzie Worsley and Roy Webb 22-11.
Two fours and a five over the middle ends were too much for Shoreham, who scored almost exclusively in singles.
Pat Edmonds, Chris Cheeseman, Bryan Bodicoat and skip Tony Beale led from the start against Marion Hoggen, Bridget Pavitt, Brian Bulmer and skip Kim Hudson, building a 10-shot cushion by the 15th.
Shoreham rallied to take the last three ends but eventually lost 16-13.
Malcolm Gardiner, Pam Duffield and skip Simon Davey gained the lead three times against Richard Pavitt, Mike Harding and skip David Goodman, who scored two shots on the 18th end to win 15-14.
If that was disappointing for Pavilion, there was worse to come in the second triples game. Alan Cheeseman, Simon Ritter and skip Ian Slater seemed to be heading for victory after 15 ends, leading David Cornwell, Dave Hoggen and skip John McMurran 16-8.
The visitors then scored three, three, four to win 18-16 and leave Pavilion's players to reflect on a spectacular collapse.
Pavilion began their 2025 Stracey Shield season in the same way they finished last year's campaign, suffering a whitewash against opponents who made the most of home advantage.
Last September a 10-0 defeat by Maltravers cost Pavilion any chance of the title. An identical outcome at Tarring Priory on Tuesday, May 13 has put Pavilion on the back foot from the start.
Priory's lawn, slower and greener than either of Pavilion's, proved too tough a challenge for many of the visiting bowlers, who frequently failed to reach the long jacks.
The aggregate score of 102 shots to 49 from the four rinks reflected the play fairly on a warm and sunny afternoon.
With Stracey matches reduced from 21 ends to 18 this year, there's less chance to overcome a big deficit, something regretted by Barry Ledger's rink of Simon Ritter, Alan Crowter and Francis Fahey when they dropped 14 shots over the first five ends.
Butch Shakespeare, Steve Davis, Steve Allen and skip Stuart Logan resisted a strong fightback and eventually won 19-16 after Logan rescued his team more than once.
Keith Lyons, Richard Berrett, John Ives and skip Tim Baldwin were 19-4 down after 12 ends against Emiliano Di Pietro, John Fairs, Jim Davis and Ray Baker. Pavilion cut the deficit with a couple of threes before losing 21-13.
Alan Cheeseman, Linda Carter, Teresa McLaughlin and skip Richard Krupa started with a three and after 10 ends were only three behind Chris Ide's rink of Derek Meechan, John Proffitt and Terry Urben. Tarring then scored a four and a five on the way to a 27-12 win.
Terry Edmondson, Sue Bryan, Bill Muir and skip Geoff Pratt trailed by three shots after six ends but were unable to make any impact from that point against Aidy Jackson, Roy Bland, Roy Barclay and skip Nick Eager, who scored a six and two fives in winning 35-8.
Not the start Pavilion wanted but the post-match drinks were most welcome after the sobering defeat.