Sadly, his opposite number, the Bosnian Serb general, Momir Talic, sent his regrets. But the gathering was otherwise a roaring success.
The deputy mayor of Banja Luka, local politicians and even a couple from the ruling Serbian Democratic Party, turned up to drink Pimms and celebrate in the Banja Luka headquarters of Nato's British forces.
Major General Michael Jackson had moved his sector HQ from the ruins of Gornji Vakuf, an early casualty of the Muslim-Croat war and a one-horse town at the best of times, to the northern city of Banja Luka.
This city was once described by the UN as "the heart of darkness", on account of the enthusiasm with which local Serbs pursued a policy of "ethnic cleansing". Ironically, it is now seen as the seat of moderate Serbs who have a constructive interest in implementing the Dayton peace plan.
Maj Gen Jackson lists his practical reasons for the move to Banja Luka. It is the only big city in his sector; it allows Nato's implementation force (I-For) to deploy one of its four headquarters in the Srpska Republic; many civilian agencies with which I-For liaises are based in the city; there is also an airport.
The High Representative, Carl Bildt, will open a regional office in Banja Luka today. He also has practical reasons. But beyond those there is a political element: those implementing the Dayton plan have been hampered since December by the hard-line Bosnian Serb leadership, which is based in the mountain village of Pale, near Sarajevo.
There has long been rivalry in the Serb camp between the big city of Banja Luka and the small town of Pale. With the eclipse of Radavan Karadzic, indicted for war crimes, and the loss of the Serb-held suburbs around Sarajevo, which was the justification for making a "capital" in Pale, Banja Luka's leaders scent victory.
Both the military and civilian authorities here welcome the arrival of Maj Gen Jackson, despite the fury in Pale. Maj Gen Jackson shrugs off the controversy. "It has been made a political issue," he said. "If they choose to make it a political issue, that's up to them."
The cocktail party was more than a social occasion. "We were quite determined about what we were trying to do," he said. "Normality is returning. You can have a drink together for a couple of hours."
I-For helicopters ferried in Bosnian leaders from Sarajevo, including Haris Silajdzic, the former prime minister and now leader of a new opposition party. Canadian troops escorted General Dudakovic from his barracks in the city of Bihac.
"It's humiliating that none of our officers is here," one local Serb said crossly. According to sources, the Pale leaders ordered General Talic and his comrades not to attend the party, even though generals Dudakovic and Talic meet frequently and cordially at military commissions chaired by I-For.
As far as the locals are concerned, the deployment of the British in Banja Luka is a good thing. The soldiers have mended roads and other infrastructure, and the I-For base employs around 100 locals and pays them in hard currency.
The presence of the British will encourage aid agencies and international organisations to spend money in the city, which was a no-go area to the UN and most foreigners in the war.
The move will hinder Pale's isolationist policy. It may also discourage visits to the city from Mr Karadzic and General Ratko Mladic, who is also indicted for war crimes. But the deployment will be low key. "We don't want tanks rolling down the high street," Maj Gen Jackson said. "We are not here as a occupying army and if we are seen to be that, we will lose credibility."