A man signs his written will, intending to give it effect, in the physical presence of his niece's husband and a neighbour, who are together throughout. Each witness then signs in the man's presence. The will leaves £20,000 to the niece and the residue to a registered charity. The neighbour has no beneficial interest under the will. There are no other witnesses, and the man makes no later will or codicil. The niece and her husband are married throughout. After the man's death, his solvent estate is administered in England and Wales. No issue of capacity or undue influence arises.
What is the effect of the witnessing on the niece's legacy?