The Land Registry has updated their Practice guide 8: execution of deeds in situations where there is only one witness to multiple signatures.

https://www.gov.uk/government/publications/execution-of-deeds/practice-guide-8-execution-of-deeds

 

Appendix 2: Examples where there is only one witness to multiple signatures

“Signed as a deed by A and B in the presence of”
Not acceptable (not clear that A and B have both signed in the presence of the sole witness
“Signed as a deed by A and B both in the presence of”
Acceptable
“Signed as a deed by A and B. Both signatures applied in the presence of”
Acceptable
“Signed as a deed on behalf of Z Ltd by A and B, both in the presence of”
Acceptable
“Signed as a deed on behalf of Z Ltd by A and B in exercise of the powers conferred by a power of attorney dated…[date]. [Signature of witness, with witness’ name and address details]”
Not acceptable (not clear that the attorneys have both signed in the presence of a sole witness).
“Signed as a deed on behalf of Z Ltd by A and B in exercise of the powers conferred by a power of attorney dated…[date]. Both signatures applied in the presence of [witness’ signature, with witness’ name and address details]”
Acceptable