As somebody who's had American submarine commanding officers sit in my office—as a commander down on the east coast—and talk to me after they've done an exercise with the Victoria class boats it's easy to make the case that our Victoria class are British-built submarines that feature some aspects that are British technology and many aspects that are American technology, including silencing and a variety of other subsystems in the submarine.
Consequently, when you put the Victoria class against British or American submarines in exercises, you tend to wind up with a draw, or with the skill of the captain perhaps determining some outcome. But they're very closely matched, except that nuclear submarines of course can go from one part of the theatre to another part at 28 knots, whereas a Victoria class takes longer to get from A to B. So they are capable boats by design.
The boats that are being built by all of the countries that build submarines at the moment are all very good products. But certainly with the modernization that's been done to the Victoria class today, there is no hesitation in turning to the government and saying “ready”.