Eclipse RCP - usage of help subsystem

Eclipse RCP - usage of help subsystem

I am developing an RCP application following the e4 development model. My
application is made of
the plugin project itself containing: the plugin.xml, application.e4xmi
and required resources
the product project with the .product descriptor
My need is to access the PlatformUI.getWorkbench().getHelpSystem() in
order to provide Help features to users. When trying to create the
Workbench itself with
PlatformUI.createAndRunWorkbench(...)
I get very low level errors like:
org.eclipse.e4.ui.model.application.descriptor.basic.impl.PartDescriptorImpl
cannot be cast to
org.eclipse.e4.ui.model.application.ui.MUIElement
Searching the web I have found little results on this same matter. I am
under the impression that an application-based product cannot access
Workbench services like the Help system, unless it is re-designed to be a
Workbench based application.
Can anyone please shed some light on how to access the workbench from a
stripped-down RCP application?
Thanks in advance