The legal position has been definitively stated by the Law Commission in their 2019 report on the subject. That report can be read here – https://www.lawcom.gov.uk/project/electronic-execution-of-documents/

Its findings can be summarised as follows:

Statement of the law: execution with an electronic signature

• An electronic signature is capable in law of being used to execute a document (including a deed) provided that (i) the person signing the document intends to authenticate the document and (ii) any formalities relating to execution of that document are satisfied.
• Such formalities may be required under a statute or statutory instrument, or may be laid down in a contract or other private law instrument under which a document is to be executed. The following are examples of formalities that might be required: (i) that the signature be witnessed; or (ii) that the signature be in a specified form (such as being handwritten).
• An electronic signature is admissible in evidence in legal proceedings.
• Common law adopts a pragmatic approach and does not prescribe any particular form or type of signature. The Courts have held that the following non-electronic forms amount to valid signatures:
  • signing with an ‘X;
  • signing with initials only;
  • using a stamp of a handwritten signature;
  • printing of a name;
  • signing with a mark, even where the party executing the mark can write; and
  • a description of the signatory if sufficiently unambiguous, such as “Your loving mother” or “Servant to Mr Sperling”.

Electronic equivalents of these non-electronic forms of signature are likely to be recognised by a court as legally valid. In practice, the following electronic forms amount to valid signatures in the case of statutory obligations to provide a signature where the statute is silent as to whether an electronic signature is acceptable:

• a name typed at the bottom of an email;
• clicking an “I accept” tick box on a website; and
• the header of a SWIFT message.
• With specific regard to deeds and the witnessing requirements thereof, a deed must be signed in the physical presence of a witness who attests the signature. This is the case even where both the person executing the deed and the witness are executing / attesting the document using an electronic signature.

So, for example, an electronic signature is legally acceptable for the purposes of a client signing a client service / fee agreement as this would be considered a simple contract. Firms requiring client authority for an advisory rebalance could accept the client’s email response as being sufficient (provided the client isn’t refusing the rebalance of course!).