None appears to have recognised them as Booker prizewinners from the 1970s that were lauded as British novel writing at its best. Of the 21 replies, all but one were rejections. Only Barbara Levy, a London literary agent, expressed an interest, and that was for Middleton’s novel. She was unimpressed by Naipaul’s book. She wrote: “We . . . thought it was quite original. In the end though I’m afraid we just weren’t quite enthusiastic enough to be able to offer to take things further.” The rejections for Middleton’s book came from major publishing houses such as Bloomsbury and Time Warner as well as well-known agents such as Christopher Little, who discovered J K Rowling.
This isn't surprising. I don't think many publishers or agents look closely at work from unknown authors. This also isn't the first time an experiment like this has been conducted. The article mentions that Doris Lessing once submitted a novel to her own publisher under a pseudonym, and it was rejected. And back in 2000, a French Magazine called Voici sent a thinly disguised version of L'Institutrice (The Primary School Teacher) by Claire Chazal (who's a celebrity French newswoman) to Plon publishing house. Plon rejected it, which was embarrassing for them since they publish it, and therefore should have recognized it.