Invisible UTR number

I've taken a new job which requires me to register as self-employed. I had been registered briefly in the past for a different job which never came to fruition so I never did any self-assessment, but I had a UTR number. I no longer what my UTR number is, so I registered again and was shown a screen saying "Self assessment registration exists. You have previously registered for self assessment. You Unique Taxpayer Reference (UTR) is:" ...but there is no UTR shown. It's just a blank space. Is there a way to find this information? Thanks

Hi Neil Rocks,
You can request your UTR be posted to you from here:
Find your UTR number
Thank you.