International Herald Tribune and Backstage mentions

Jennifer Ehle is mentioned in passing at Backstage.com (and again called a "British actress").

Thankfully, the International Herald Tribune gets it right, and appreciates her performance as well.

The Philadelphia Story," the 1939 American comedy by Philip Barry newly revived at the Old Vic, gets the hardest part right: finding an actress to play the tricky central role of the Philadelphia socialite Tracy Lord who can banish memories of the role's legendary stage and screen originator, Katharine Hepburn. It's not just that Hepburn's inimitable voice seems etched into such exclamations as "Golly Moses," with which Tracy greets the goings-on in her elegant family home on the eve of her second wedding. But class and breeding, too, can be hard to communicate on stage these days without it looking as if you're commenting on the role. All praise, then, to Jennifer Ehle, who has stepped up to a rather daunting task and provides the one unalloyed bright spot of an otherwise dullish evening.
...
Thank heavens, then, for Ehle, the Anglo-American actress (her mother is the British-born Broadway mainstay, Rosemary Harris) returning to the London stage for the first time in five years, her natural authority only deepened over time. While the writing itself can tilt toward archness, Ehle is always real, as she ricochets between at least three suitors, an errant father, and a terrifyingly precocious younger sister. And at the end, when her character melts, the audience does, too. Whereas "Billy Elliot" is about a young boy who finds a new life, "The Philadelphia Story" tells of a heroine who, much to her own surprise, discovers a new self.