I've stumbled upon this as a solution:
<xp:tabbedPanel id="lotusLinks" styleClass="lotusInlinelist lotusLinks">
<xp:this.selectedTab><![CDATA[#{javascript:param.tab;}]]></xp:this.selectedTab>
<xp:tabPanel label="Home" id="tabHome" href="documents.xsp?tab=tabHome"
selectedTabStyleClass="lotusSelected"
startTabStyleClass="lotusFirst">
</xp:tabPanel>
<xp:tabPanel label="Websites" id="tabWebsites" href="websites.xsp?tab=tabWebsites"
selectedTabStyleClass="lotusSelected">
</xp:tabPanel>
<xp:tabPanel label="System Set Up" id="tabSystemSetUp" href="systemsetup.xsp?tab=tabSystem"
selectedTabStyleClass="lotusSelected">
</xp:tabPanel>
</xp:tabbedPanel>
I have set the default open tab as a computed value:
param.tab;
Question: Is this the best solution or am I missing something fundamental about the tabbed panel control?
Many thanks