Apple ID locked, please help urgently

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Hello, if had my @icloud.com email for a long time now, however just the other day I revived an email saying that it has been locked for security reasons, however I would try and recover it but I no longer have access to my recovery email, or my security questions as they were not created by me but rather by someone who I can no longer talk to. And also all of my other major accounts are linked to iClou.

I can provide proof that this is my account, but how can I do so.

it would be greatly appreciated if you could leave a message telling me what I could do,

Thanks