According to the Business Insolvency Helpline the advertisement can appear 'as early as seven business days from service' (of petition) so that implies it could be longer.rabidbee Sorry, you're right and I'm wrong. It will appear in the Gazette seven days after a court hearing date is set, according to the Gazette.
https://www.thegazette.co.uk/all-notices/content/100380
What to do if have received a HRMC winding up petition?
If you have received a winding up petition from HMRC, you should not ignore it. The next step will be a court hearing and your company could be wound up and put into compulsory liquidation. You must act quickly and one key date to look at is the date of the winding up hearing, but this does not represent how much time you have to take action, as, for example, the petition can be advertised as early as seven business days from service. Advertisement of the petition will freeze your bank accounts.
Either way and for whatever reason, a search of The London Gazette would suggest it hasn't yet been advertised.