(DingDong) Ladies and gentlemen, your captain speaking:
We have just arrived at our cruise altitude of 35,000 feet, popularly known as
"the coffin corner"'. Enjoy your flight with XYZ Airlines ...
EDIT:: Just to put Martin Alder's remark in the BBC documentary into perspective: in this case as shown in the graphic, the 'coffin corner' is actually 102 kt wide: from M=0,58/192 ktCAS to M=0,86/294 ktCAS.
HN39