Removing number from Heading 1, leave rest alone

Greetings,

I have a document with the following heading numbering system:

1 Heading 1
1.1 Heading 2
1.1.1 Heading 3

Fairly straightforward. However, I would like to remove the number in front of Heading 1. Attempts to do this in Bullets and Numbering by
removing the number in Number Format for Level 1 causes all the lower levels to omit the number also. Is there a way to restrict this to one
heading style only?

TIA,
-Mark