I have been waiting for Radio 3 to get to this. At the start of the year the station promised to play all of Handel's operas. This one is based on the Battle of Teutoburg Forest and Arminius. So successful was it that it only managed six performances! Here is Suzanne Aspden andthe Radio 3 blog on the opera:
You have to have stamina to work your way through Handel's operas. Having enjoyed the delightful magical and pastoral scenes of the operas broadcast in the Handel Opera Cycle in the past few weeks - Orlando, Alcina, Atalanta - we're now back to more traditional heroic stuff with Arminio (1737), this week. It tells the story (from Tacitus) of warfare between the Romans and the Germans (the barbarian invaders, in other words), with the German tribal ruler Hermann (Arminius) betrayed into captivity by the collaborator, Segestes, but ultimately triumphant.
The German theme may have meant the opera was intended to honour the Hanoverian monarchy. Perhaps Handel was inspired in that direction by his recent success with the delightful pastoral opera, Atalanta, written to celebrate the wedding of the Prince of Wales. Or perhaps he was hoping to ingratiate himself for financial reward - after all, he was still doing battle himself against the so-called 'Opera of the Nobility', who were occupying the opera house, and just as keen to curry favour with the royal family.
You can listen to the opera here. That link lasts for another couple of days. Recommended.