Action Template Mailto subject and body

We have been trying to use the substitution keywords to get a mailto link to send to customers through an action template that sends an email to our mailboxreader/etm

This is mostly working, we can get the  event reference in the subject line,  but cannot get the substitution keywords to populate the body of the mailto.

we have tried a few things and its so close but just doesnt put the subject/body in the right place, seems to not be picking up the ? correctly

if we do  this it works great, without a body of the email

<vtl>#set($eventLink = "mailto:XXX@test.com?subject=Approved Ref:")</vtl>
<a href="$eventLink$new.event.formattedReference">approve</a>
 

to try to get the body in we tried

<vtl>#set($eventLink = "mailto:XXX@test.com?subject=Approved Ref:")</vtl>
<vtl>#set($eventLink2 = "?body= Approved%0A%0DAdd%20Additional%20comments%20below%20if%20required")</vtl>
<a href="$eventLink$new.event.formattedReference$eventLink2">approve</a>

and got  this in the subject with nothing in the body

Approved Ref:S999999?body=Approved

also tried swapping it round and got stuff n the body but no subject

<vtl>#set($eventLink = "mailto:XXX@test.com?body= Approved%0A%0DAdd%20Additional%20comments%20below%20if%20required?subject='Ref:'")</vtl>
<a href="$eventLink$new.event.formattedReference">approve</a>

Has anyone managed to get a mailto link working within the action templates/substitution keywords to populate the subject and body of the email

Thanks