Can I sign the invitation letter for visiting relatives in Britain electronically?

Of course. Invitations to visit relatives in Britain can be signed electronically. The applicant needs to provide two scanned copies: an application form with electronic signature and an invitation letter with the applicant's original signature to prove the authenticity of the two documents. The applicant must sign the original invitation letter, and the electronic signature is limited to the application form, so that the immigration officer can confirm the safety when handling the application.