The Corkman was among 16 to make the jump-off from a starting line-up of 45 and, early into the fray, he grabbed the lead with a clear round in 38 seconds.
As rider after rider failed to match the veteran mare’s pace, it looked like Twomey could net the top prize.
However, with just three rivals left to go, it was time for the French to delight the home crowd, firstly with Simon Delestre (Hermes Ryan) crossing the finish line in 37.94secs, before Patrice Delaveau powered to victory in 36.08secs when last to go on Lacrimoso 3 HDC.
“She’s been a really good servant to me for many years,” said Nottinghamshire-based Twomey of the mare, which he jointly owns with Sue Davies.
Bertram Allen was in second gear in Paris compared to his three-car winning streak days earlier in Sweden.
His best result in the French capital came in Saturday’s Gucci Gold Cup, in which he finished fourth with Quiet Easy 4.
The class saw the top 10 from the 28 starters go through to the second round, starting on a clean sheet. As a result, the need for speed meant only three riders produced clears in the opening round, with Allen into the decider as the fastest of the first-round four-faulters. The Wexford rider went on to replicate his first-round display, which proved good enough to earn him €10,000.
At the four-star show in Salzburg, Austria, Shane Breen won a 1.50mtr speed class aboard his latest acquisition, Undicci.
The Tipperary rider and the 11-year-old gelding - which was previously owned by Sweden’s Malin Baryard and campaigned by Mathijs van Asten of the Netherlands - finished almost three-quarters-of-a second ahead of runner-up Olivier Robert (Quenelle du Py).
At the two-star show at Opglabbeek in Belgium, Cian O’Connor claimed the top prize in the grand prix qualifier with his new horse Crespo PKZ, while second place also went to Ireland, with Jack Dodd just under two seconds behind on Wrangler II.
Meanwhile, Horse Sport Ireland has confirmed that Tom Slattery has brought to an end his successful stint as high-performance coach of the Irish pony show jumping team. The Galway man has moved to the UK, training at Manton Grange stables, Marlborough, Wiltshire, owned by American Fred Goltz.