The simplest way to close your LSE Public Account is to login to LSE for You and use the 'Close Account' option.
Alternatively, you can use this form to request a 'one time password' that will allow you to close your account. This will be sent to the email address you gave to be the username of your account.
If you no longer have access to the mailbox for the email address that is your username, have forgotten your password (so can't login to LSE for You) and have also forgotten the answers to your reset password security questions, then we will have to close the account for you. If you are an applicant, contact the relevant admissions department. If you are an alumni, contact Student Services.