At page 143, paragraph 8.111 of the Companion says:
“The proceedings and forms of words for amendments and clauses in Grand Committee are identical to those in a Committee of the whole House save that no votes may take place. Normally only one bill per day may be considered in Grand Committee. Amendments, which may be tabled and spoken to by any member, are published and circulated as for Committee of the whole House”.
Paragraph 8.112 says:
“As divisions are not permitted in Grand Committee, decisions to alter the bill may only be made by unanimity. Thus when the Question is put, a single voice against an amendment causes the amendment to be negatived”.
I am that single voice.