Prefix Subject with Postmaster Filter

[gob]

Hi
I want to add a prefix to the Subject line of an incoming email on a specific queue.
I have managed to add the prefix by setting X-OTRS-Title and the prefix appears but I cannot get it to be followed by the original subject.
Through my research I have tried the following:
[***] - adds the "To:" email address after the prefix

Anything else just repeats the text set in the filter such as:
[Subject] - just adds "[Subject]
[<OTRS_CUSTOMER_SUBJECT[30]>]

Any suggestions?