Hi Alice: - Considering the very well known fact that Celts were settled on the Britannic Island Kingdom for well over 6000 years and were far far better educated than the so called Romans who brought not Pax Romana but POX Romana to this area - were as usual ONLY looking for gold to finance some idiot back in Rome.
Its an olde story - the Romans sacked Jerusalem and the Temple of David ONLY for the gold and silver they could melt down to build their Colosseum which to the Celtic Grand Marshall Brennus became known as the Roman "Crematorium" used for nearly 9 years filled with the "Facia Bundles" known as bundles of twigs to burn the bodies of over 15000 dead Romans - then the march was on to destroy the Gauls well known for their gold and figured every Celtic Kingdom just had more of the stuff. So began the "March of the Facist"
I suggest that you STOP referring to the Celts as if they were something less than the Roman army. They- the Celtic armies were vastly superior to the Roman army made up of largely illiterate buffoons.
Second Last point - obviously you didn't go to Oxford - get your mt-dna tested and like Dr. Brian Sikes now Dr. Bryan Sykes and Graham Webster who after I called him changed his tune right in the middle of his book on the Wrekin Capital of the Cornovii - to accept the Romans for who they were especially - AND when they found the grave and headstone under the market place in Chester of the famous Celtic Commander from Dal'Riata known as "Cunerix" who arrived at the request of the Commander of the Wrekin along with 87 very well trained Celtic Wolf Hounds and 300 Celtic Warriors and won.
Last Point - Ancient Galatians used stone slings with whistling stones when they fought the Assyrians - in fact the Celts used molded "stones" as the ones you showed were classically inaccurate and the rate at which they lost any effectiveness was well documented.
Romans marched with camp followers - put to death by the Celts as a health issue AND the CELTS marched with "Field Doctors" also well documented - your points of reference are WELL OFF THE MARK.
If the Romans were SO GOOD then why did they take well over a 100 years to get into Britannia - Romans lousy sailers - Battle of Quiberon Bay. Their ships were so god that they asked the Celtic ship yards to build some for them - read the writings of Brutus who sat on the hills watching the battle and on it goes -- get your mtdna tested kiddo -
University of Toronto