Hello!
Reading A Wolf Hall by Hilary Mantel, I found this phrase: At his back a troupe of painted nymphs are frisking in a glade.
Is it grammatically correct to use "are" here? I believe it should be "is", because the troupe is frisking, and "of nymphs" is part of an extended noun.
I would be grateful for your opinion.
Thank you!
I agree with you.
Dick said
I agree with you.
Thank you! Shall we inform Ms. Mantel? 
That book was WINNER OF THE 2009 MAN BOOKER PRIZE, WINNER OF THE NATIONAL BOOK CRITICS CIRCLE AWARD FOR FICTION, A NEW YORK TIMES BESTSELLER, and Amazon's "Best of the Month" for October 2009.
If word gets out that using a plural verb with a singular subject can have thoe results, authors is gonna perpetrate syntactical terrorism on their readers.
I believe that in British English it is fairly common for a plural verb form to be used with a collective noun. Particularly so where the intent of the sentence is that the members comprising the group are functioning as individuals: The army were pitching their tents or The cast were learning their roles. It's not a huge stretch to see that the army is made up of soldiers, and that a cast is a bunch of actors – who most assuredly act as individuals even when acting together! English is very often not logical, and when it is, different logic may apply in its different branches.
Consider: The Pittsburgh Pirates were hot that year. The team was on fire. Pittsburgh was sure to win the pennant. The Pirates were the team to beat.
All four sentences are referring to exactly the same thing, but in two cases it's singular, in two it's plural. Does that make any sense? I believe that standard British usage is the plural in all these cases.
Consider: Dame Hilary has rather strong credentials as a writer. If you wanna correct her choices, go right ahead.