CAS-T Class D for Royalty

[Jim59]

Class D CAS-T established for a royal flight can only be entered if a clearance is given by ATC. However, I seem to remember that such clearances cannot be given to sailplanes.
I've done an extensive search of the ANO, AIP, MATS Part 1 etc. and cannot find this restriction. Does it still exist or has it been lifted?

[sambatc]

Class D CAS-T established for a royal flight can only be entered if a clearance is given by ATC. However, I seem to remember that such clearances cannot be given to sailplanes.
I've done an extensive search of the ANO, AIP, MATS Part 1 etc. and cannot find this restriction. Does it still exist or has it been lifted?

Sailplanes can be cleared into class D airspace, yes