Whether the same is true for British jurisprudence I do not know.
Can't speak for U.S. jurisprudence*, but one can cross-examine one's own witness under english jurisprudence if you can convince the court that the witness is "hostile".
Absent that liberty, you would have little opportunity to impugn the witness' testimony if it couldn't be impugned by any other means.
The exception to the rule against cross-examining your own witness is made because the witness isn't really 'your' witness.
You have called the witness because his/her evidence is critical to your case, but the witness is also demonstrably hostile to your case.
Obviously, the other side will never call the witness, knowing the witness would be exposed to cross-examination.
Rules which do not serve the ultimate ends of justice are arbitrary and unjust, I would argue, in any jurisdiction.
Of course, the court can be expected to impose limitations on the right to cross-examine in these circumstances.
*Perhaps I spoke too soon. I just found the following on the Internet.
National Institute for Trial Advocacy
Part 03 - Cross Examining the Hostile Witness
0.75 Hour Credit valid until January 1, 2004
Brought to you by the NITA
Author: Irving Younger
This course has been approved for Credit in the states of Arizona, Missouri, California, New York, and Colorado.
Perhaps "cross-examining the hostile witness" is not an option in every state, tho I can't imagine why any state would preclude the practice altogether.
[BTW I had the pleasure of attending several of Irving Younger's Trial Advocacy symposiums at the University of Michigan at Ann Arbor some years ago.
It was always a fabulous treat to see the great names of American litigation performing their assigned roles on stage.
"Performing" is a word I use quite deliberately because one famous litigator actually insisted that a successful trial lawyer should be a "good actor". I guess we always knew that, but who expected any lawyer to actually admit it, nay, proclaim it as a virtue?]
