Can't get extended display on Windows 10

Intel(R) HD Graphics 5300
'This device is working properly'
Driver: Intel Corporation. 18 Nov 2015

Updated just now.
Problem still there.

Worth mentioning - when I click Apply on 'Extend these displays' the screen on my laptop goes blank. Also I can't see the 'Keep these settings' dialog and it reverts back after 15 seconds as if I clicked 'No'.

Does it really go blank or maybe just black? Move the mouse pointer over the edges of the display to see if it maybe extends correctly after all.

Also try to feed the external display only. Switching between clone and extend and external/internal only can be done by pressing winkey + p

Yes. It is black, rather than blank. Moving the cursor to the edge it goes beyond the edge (stops at the other edge). But can't see the cursor as the laptop monitor is black.

Win +P gives a dialog I haven't seen before. So the options there all work, EXCEPT for Extend Display.

Extended Display worked before the reinstallation.
Reinstalled from the recovery partition (Windows 8) , then it went into the automatic Windows 10 upgrade. (laptop bought in Nov).
Yes it supports 4K res. My Lenovo Yoga Pro 2 works fine with same 4K monitor.

Rather than first installing 8, then upgrading, Install Windows 10 directly by booting from the November iso, which you can put onto a USB stick using the tool WinSetupFromUSB:

https://www.microsoft.com/software-download/windows10ISO

http://www.winsetupfromusb.com/

Make sure you install the correct version (Home or Pro, depending on what is installed now). When you get asked for the product key click on "I don't have a Product Key". Since your PC has already successfully been activated with the m$ servers and registered there, it will activate again automatically once you have an internet connection.

Once the OS is installed, and if it is available for Windows 10, install the chipset drivers, and if Windows Updates doesn't automatically find and install the other drivers (you'll have to wait some time and probably also a couple of reboots for that to finish, so be patient if it doesn't happen immediately), download and install the rest of the needed drivers.

After that check if you can now extend your displays.

rindi, that's the ultimate test. The Windows 10 was downloaded by the Lenovo only yesterday. So wouldn't that be the latest Windows 10 release?
I'll try it (a complete fresh install) if I don't have a solution within the next few days. Thanks.

It would be the latest, but it depends if you have downloaded it as an iso or not.

Thanks for your help everyone.
I solved it by reinstalling Factory Reset and Windows 10 Upgrade - one more time. But this time I disconnected the external monitor while reset/reinstalling.. That seems to have been the problem, though I don't know why.

It's the solution that worked for me in this case. It may help others to try that first, and then dig deeper as suggested by the experts.

The lesson learned is, when installing an OS (or reinstalling/factory reset etc)  disconnect all peripherals.