Creating a New Version of a Record using the ServiceAPI

I can create Records and upload electronic documents to them using the .NET wrapper around the service API.

Our next requirement is to be able to create a version of a Record, but I cannot see an obvious way to get it to work.

I have tried using the MakeNewRevision property on the record and reposting, but this doesn't work. 

I then tried looking at what the WebClient does to create a new version, - it seems to post a RecNewVersion action to the webclient, to the Record endpoint, but it's not obvious how that maps back to Service API calls. I can't see an ServiceAction for Record that matches that name (or anything similar).

Any suggestions as to how you create a new version using the .NET wrapper around the service api would be appreciated ?