Windows Defender Service fails to start. Exits with code 0x800106ba

I discovered this problem when Windows Security Center notified me that I had no virus protection. I have just (as in less than 24 hours ago) done a clean install of Windows 10 onto my ASUS X205TA notebook. The only applications that have been installed since then have been Chrome and OneNote (desktop). 

If I start the service while Windows Defender is open, I get the following error popup:

If Windows Defender is not open and I start the service I get the following error in the Message Logs:

Log Name:      System

Source:        Service Control Manager

Date:          16/06/11 18:50:30

Event ID:      7023

Task Category: None

Level:         Error

Keywords:      Classic

User:          N/A

Computer:      mycomputername

Description:

The Windows Defender Service service terminated with the following error: 

General access denied error

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

  <System>

    <Provider Name="Service Control Manager" Guid="{555908d1-a6d7-4695-8e1e-26931d2012f4}" EventSourceName="Service Control Manager" />

    <EventID Qualifiers="49152">7023</EventID>

    <Version>0</Version>

    <Level>2</Level>

    <Task>0</Task>

    <Opcode>0</Opcode>

    <Keywords>0x8080000000000000</Keywords>

    <TimeCreated SystemTime="2016-06-11T22:50:30.547593900Z" />

    <EventRecordID>1114</EventRecordID>

    <Correlation />

    <Execution ProcessID="776" ThreadID="7800" />

    <Channel>System</Channel>

    <Computer>mycomputername</Computer>

    <Security />

  </System>

  <EventData>

    <Data Name="param1">Windows Defender Service</Data>

    <Data Name="param2">%%2147942405</Data>

    <Binary>570069006E0044006500660065006E0064000000</Binary>

  </EventData>

</Event>

I followed the advice from http://answers.microsoft.problems-starting-windows-defender-in-windows/808253bb-db89-4db9-a4e5-1c91a86489e9 and can report the following.

• PC has been rebooted.
• No antivirus software had been installed prior to the appearance of this problem. I subsequently installed MBAM as an additional screen to ensure I had not somehow picked up some malware.
• Scan with Microsoft Safety Scanner found nothing. I also installed and scanned with MBAM.
• SFC found no corrupted files.
• Restart of Security Center Service did not help.

I'm out of ideas now.