When Did PG Tips Invent Tetrahedron Tea Bags?

When did PG Tips invent tetrahedron tea bags?  Tetrahedron is another word for pyramid-shaped.  Actually, PG Tips launched pyramid-shaped (tetrahedron) tea bags in 1996.  This shape was chosen because it helps the tea leaves move more freely, which creates a better cup of tea.   In what may be an urban legend, this design also was chosen because a corner of the tea bag usually will be above the water line, which allows workers such as builders, easily remove the bag without the need for a spoon. Whether this last part is true, we will try to find out.

What do you think?