Port cinques beneath Horsham onslaught

First off, thanks to Phil for the top quality pun. Secondly, I can report success for Horsham in the farthest-flung corner of Sussex...

Horsham 1 travelled to Hastings for an away match against their first team, which had previously scored 3/3 in the division and were therefore opposition to be respected. We managed a traffic-free journey down and faced a strong Hastings lineup.

On board 2 I was first to finish in ignominious fashion, having an uninteresting but acceptable position one moment and a lost one a couple of moves later. Francis Rayner took full advantage with a smart knight move and I was toast. Clearly however my demise spurred my team to take revenge for their captain, as we never seemed in trouble on any of the other boards and pushed hard for the wins. Gavin's advanced passed pawn proved decisive against John Sugden on board 1, and Black's entombed knight on a8 didn't help matters either. Gavin won the exchange and John resigned before White's a-pawn could promote. On board 5 Paul and Ollie Willson played a Sicilian in which Ollie seemed to equalise straightforwardly but there did not seem to be much more than that and a draw was the fair result.

On board 3 Dix steadily improved his position against Alfredo Luaces in what he later described as a 'tactic-free game'. After going two pawns up Dix was nonplussed by a draw claim from Black - once we had determined that the position had only been repeated twice Alfredo resigned. This just left Phil who had nicely dissolved Jerry Anstead's centre with a timely b5 temporary pawn sacrifice and won a pawn in the ensuing complications. This game is still unresolved but Phil has at least a draw so the final result will either be 3-2 or 3.5-1.5 to Horsham.

J.N. Sugden 0-1 G.R. Lock
F. Rayner 1-0 A.R.J. Higgs
A. Luaces 0-1 D.N. Roberts
J. Anstead A-A P. Stimpson
O. Willson 1/2-1/2 P. Taylor

Time for a puzzle. The above diagram shows Rayner-Higgs with Black to move. After some thought, I resigned. Why? Answer will be posted below in the comments.