Possible to change the start cover date of an approved ToR?

Hello, I got a ToR approved recently but there's a chance I might arrive in England a few weeks before the the cover start date. Is it possible to change it? A lot of articles state it should be valid a month before as well but the document doesn't mention that?

Hi,
 

I would advise contacting the Customs and International trade helpline on 0300 322 9434 if you have any other issues with your query. Thank you.