Some articles on st, diagonal st, diagonals:
Union Jack - Design - Specification
... three component crosses that make up the Union Flag are sized as follows The red St George's Cross width is 1⁄5 of the flag's height with a 1⁄15 flag height fimbriation The white diagonal St Andrew's ... The crosses are slightly pinwheeled with St Andrew's Cross leading in the clockwise direction ... The centre-lines of the diagonals must meet in the centre (as shown on the diagram) ...
... three component crosses that make up the Union Flag are sized as follows The red St George's Cross width is 1⁄5 of the flag's height with a 1⁄15 flag height fimbriation The white diagonal St Andrew's ... The crosses are slightly pinwheeled with St Andrew's Cross leading in the clockwise direction ... The centre-lines of the diagonals must meet in the centre (as shown on the diagram) ...