There is now a body of case law which softens the absolute 13 month time limit see paragraph 6 of KD v SSWP [2021] UKUT 329 (AAC)
6 It had been generally assumed that the 13-month backstop rule was absolute: see LS v London Borough of Lambeth (HB) [2010] UKUT 461 (AAC); [2011] AACR 27 at [130]. However, the Supreme Court in Pomiechowski v Poland [2012] UKSC 20 decided that apparently absolute time limits may, in some limited circumstances, have to yield to the requirements of Article 6 of the ECHR (following its incorporation into UK law by the Human Rights Act 1998). This discretion to extend an absolute time limit can only arise “in exceptional circumstances” and where the appellant “personally has done all he can to bring [the appeal] timeously” (see also the Court of Appeal’s decision in Adesina v Nursing and Midwifery Council [2013] EWCA Civ 818). This is a very recognised as being a very narrow test to have to meet.
Any adjudicating authority may disapply secondary legislation if it breaches a convention right ( RR (Appellant) v Secretary of State for Work and Pensions (Respondent) [2019] UKSC 52) so its worth trying the late application route and taking it through to appeal (although it will be a very long shot)
[ Edited: 7 Feb 2023 at 11:18 am by Stainsby ]