I've seen that a portion of the GWML has suddenly been closed for "emergency track repairs". Services are showing as being removed from the timetable at short notice (VCN in RTT).
The Heathrow Express live status page shows this, but doesn't suggest there is any ticket acceptance, let alone give any advice on the alternative transport they refer to:

The TfL live status page for the Elizabeth line only shows the planned reduction in frequency as a result of the usual Sunday 2-track railway. It doesn't say anything about the sudden closure:

Clearly there isn't a complete closure of the GWML as GWR services to/from Paddington are still running (subject to the usual Sunday driver shortages, of course). So what exactly has been closed - is it just the Heathrow branch?
Why has this happened with little to no prior notice, and a complete lack of information on the TfL live status page? Why is there no ticket acceptance or replacement bus service in operation? Not all journeys are adequately served by the Tube or service buses.
Many Heathrow shift workers, and a good number of airline passengers, rely on the last trains of the day. It's unacceptable to simply strand them, but this seems to be becoming increasingly common in my experience of using Heathrow.
I'm lucky not to be stranded tonight myself, but that's only because my flight arrived considerably early. Had it arrived on time, I may have had a problem...
To add insult to injury, increases of up to 16% have come into effect today for many TfL-rate journeys that avoid Zone 1...
The Heathrow Express live status page shows this, but doesn't suggest there is any ticket acceptance, let alone give any advice on the alternative transport they refer to:

The TfL live status page for the Elizabeth line only shows the planned reduction in frequency as a result of the usual Sunday 2-track railway. It doesn't say anything about the sudden closure:

Clearly there isn't a complete closure of the GWML as GWR services to/from Paddington are still running (subject to the usual Sunday driver shortages, of course). So what exactly has been closed - is it just the Heathrow branch?
Why has this happened with little to no prior notice, and a complete lack of information on the TfL live status page? Why is there no ticket acceptance or replacement bus service in operation? Not all journeys are adequately served by the Tube or service buses.
Many Heathrow shift workers, and a good number of airline passengers, rely on the last trains of the day. It's unacceptable to simply strand them, but this seems to be becoming increasingly common in my experience of using Heathrow.
I'm lucky not to be stranded tonight myself, but that's only because my flight arrived considerably early. Had it arrived on time, I may have had a problem...
To add insult to injury, increases of up to 16% have come into effect today for many TfL-rate journeys that avoid Zone 1...