Source: pp 185-186, The Art of the Advocate (1993) by Richard Du Cann QC (called to the Bar of England and Wales).
Juries have no rights on questions of evidence at all, except as the final arbiters of fact. It is one Of the contradictions Of English legal procedure that those who are required to decide questions of fact have no power to require fact to be laid before them. They can, of course, ask questions. But they cannot require witnesses to be called to answer them, or even insist that witnesses Who are called do answer them. (Grand juries had power to do both. They were abolished in 1933.) This may be a shock for layman who believes in the infallibility of the jury system without understanding what a jury undertakes to do. Their oath return a verdict, 'according to the evidence'. Their oath is not to return a verdict, 'according to the evidence which We think should be called'. so, if the question they ask requests information which by the laws of evidence is inadmissible (for instance, in a criminal trial, 'has the defendant done this before?'), then it cannot be answered. Put more shortly, they cannot ask questions which could not be asked by the Judge or either of the advocate.
[1.] As a rule questions come from the jury after they have retired to consider their verdict, when they cannot be answered. This may seem harsh. But the line must be drawn somewhere.
There must be a point when no further evidence can possibly be called by whatever name it may be known. That point is reached when the Judge finishes his summing-up.