I have data like this first image,

where for each id there can be more than one letter, and all the other columns are just repeating the same information. (Excuse the crudeness of my image.)
My aim is to get a report in the report designer like this:

I have a table with all the columns as nested row groups.
The first id column, because it is a group, shows the id's in large (across rows) boxes. However, foo, bar, etc., all show individual cells, with grey borders. The cells are not merging.
I understand the behaviour, kind of, because the letters in the previous columns are individual, not a grouped collection.
If I were to reorder the columns it would work but I cannot do this; they must appear in the original order. Nor does Hide Duplicates work because the are not duplicated across a letter.
Can you suggest how I might get the desired output?