...and [for anyone interested] a cut-down version of BitLocker is automatically (and apparently silently) enabled where supported:
https://docs.microsoft.com/en-us/windows/security/information-protection/bitlocker/bitlocker-device-encryption-overview-windows-10#bitlocker-device-encryption
Something seems to have upset it though.  As I can't find reports of such things on a larger scale, I suppose it probably isn't "necessarily" an update bug.
Kind regards,
Gareth
On Thu, 21 Jan 2021, at 23:54, Gareth Evans via Hampshire wrote:
> Apologies for all the messages - writing while researching.
> 
> m3datarecovery doesn't seem to have a huge following so not sure about that.
> 
> I know this isn't really the place (forgive me, and my original 
> question about dislocker (or other Linux techniques) still stands...) - 
> any recommendations appreciated.  
> 
> Thanks,
> Gareth
> 
> 
> On Thu, 21 Jan 2021, at 23:04, Gareth Evans via Hampshire wrote:
> > I meant to say "Windows software" - it isn't by MS.
> > 
> > 
> > On Thu, 21 Jan 2021, at 21:43, Gareth Evans via Hampshire wrote:
> > > Hello,
> > > 
> > > A friend with a Windows laptop recently found that BitLocker was 
> > > activated after applying
> > > 
> > > https://support.microsoft.com/en-us/topic/security-update-for-secure-boot-dbx-january-12-2021-f08c6b00-a850-e595-6147-d0c32ead81e2
> > > 
> > > (this seems to be a thing - 
> > > https://www.google.com/search?client=firefox-b-e&q=windows+update+activates+bitlocker )
> > > 
> > > but it didn't accept the correct recovery key.
> > > 
> > > A quick Google suggests this means bitlocker is corrupted.
> > > 
> > > There is some MS software which will hopefully perform recovery [see 
> > > solution 5 in...]
> > > 
> > > https://www.m3datarecovery.com/bitlocker-drive-data-recovery/bitlocker-not-recognize-password-or-recovery-key.html
> > > 
> > > - is there any likelihood that dislocker on Linux may be of use?  
> > > 
> > > Does anyone have experience with this sort of thing?
> > > 
> > > Thanks,
> > > Gareth
> > > 
> > > -- 
> > > Please post to: Hampshire@???
> > > Web Interface: https://mailman.lug.org.uk/mailman/listinfo/hampshire
> > > LUG URL: http://www.hantslug.org.uk
> > > --------------------------------------------------------------
> > 
> > -- 
> > Please post to: Hampshire@???
> > Web Interface: https://mailman.lug.org.uk/mailman/listinfo/hampshire
> > LUG URL: http://www.hantslug.org.uk
> > --------------------------------------------------------------
> 
> -- 
> Please post to: Hampshire@???
> Web Interface: https://mailman.lug.org.uk/mailman/listinfo/hampshire
> LUG URL: http://www.hantslug.org.uk
> --------------------------------------------------------------
-- 
Please post to: Hampshire@???
Web Interface: 
https://mailman.lug.org.uk/mailman/listinfo/hampshire
LUG URL: 
http://www.hantslug.org.uk
--------------------------------------------------------------