Is part of the delay down to confirming the legality of stopping a British citizen from returning to the UK (if they don’t have a test / fail a test). This was being debated in the KLM forum after the Dutch govt brought in a similar rule last week and indeed it was challenged in the Dutch Supreme Court
Here in Ireland, the requirement for a negative PCR test is currently confirmed to travellers from UK & South Africa (useless on so many levels I know) but the plan appears to be to bring in a PCR test for anyone coming from somewhere outside of the EU green list (pretty much nowhere) but there appears to be a concern on how constitutional it may be to deny an Irish citizen the right to return home