Sorry Beryl but I have to disagree.
Nowadays, both flags are used side by side to commemorate St David's Day and the Gold and Black colours have been synonymous with the Patron Saint of Wales for centuries in the same way as the current Red Dragon on a green and white background was introduced by Henry Tudor.
I consider the Welsh Flag to be the National Flag but I also consider that the Cross of St David can be used in the same way as the crosses of St Andrew, St Patrick and St George when they are unfurled on their Saints Days.
Randa