SQLAgent XPs disabled after repair of MSSQL 2008 R2

After running a repair on MSSQL 2008 R2 you may find that the SQLAgent does not start up and indicates "Agent XPs Disabled" in SSMS. The following steps can be used to try and resolve this issue:

Configure XPs Option

sp_configure 'show advanced options',1
go
reconfigure with override
go
sp_configure 'Agent XPs',1
go
reconfigure with override
go
sp_configure 'show advanced options',0
go
reconfigure with override
go

Security Groups

Ensure that the startup account of SQLAgent is part of the sysadmin group. Ensure that the SQLAgent startup account is a member of the local Windows group on the server called SQLServerSQLAgentUser$ServerName$InstanceName.

After our repair, all the above steps were required. Step 3 wasn't found in any article online, but only by going through all the options available.