How to insert an additional header row in a table?

I'm setting up a report in PowerBI, trying to match the formatting of an existing report, but can't see how to insert text in or over my column headers:

The header should look like:

Name | ID | Date of Birth   | Sex | 

     |    | dd | Mon | YYYY |     |

(where the column names are coloured) 

It's simple to do this in excel, but I can't see how to do it in PowerBI.