Throughout, he gave every note its due weight in what, with other players, might have been mere passagework.
For a few lines in a rapture-filled Larghetto, he created a magical quintet with clarinets and bassoons.
The violinist did not relax at encore time, with the Ernst transcription of Schubert's Erlking. Ingeniously conceived and not without some subtleties, the piece also has its circus-like aspects.
Indeed, there was a ripple of laughter during what is the most poignant moment in Schubert's original - curiously justified, when, after all the fireworks, the piece ends with a casual, throwaway phrase.
Before interval, with Mendelssohn's Ruy Blas overture, Portal threw aside any potential plod lurking in its stolid pages to thrill us with gutsy brass and volatile, rushing strings.
The conductor also made sure the composer's Italian Symphony was blithe and sunny throughout. It was full of telling detail, from Peter Facer's sprightly oboe coaxing us back for a first movement repeat to the effervescent zing of Mendelssohn's closing saltarello.
Just a week ago, the APO almost managed a full house for Bach's Mass in B minor; tonight also came tantalisingly close, with the extra bonus of a very visible younger contingent in the audience.
What: Auckland Philharmonia Orchestra
Where: Auckland Town Hall