It should have been posted in the "Customers" forum, but no worries I've moved it.
Before commenting though I should make you aware as per the note on every page of the website, we aren't Royal Mail and therefore what we say here is not done so in an official capacity. For an official response you would need to contact Royal Mail direct - try their twitter feed @royalmail.
I have checked your tracking code in Royal Mail track and trace https://www.royalmail.com/track-your-item#/
and it doesn't recognise the number, so, unfortunately, there is not much we can do to advise you here.
We have no affiliation with either Royal Mail or the Communications Workers Union (CWU), except that most of our members work for Royal Mail and/or are members of the CWU.