The question of whether it was real or not is a moot point as far as I'm concerned.
David Brown's comment nails it for me; these weren't tears for the soliders and civilians killed based on apalling evidence which was - at best - hopelessly interpreted - or at worst deliberately spun to argue the case for war.
These were tears for the stresses and burden he feels. Well tough shit. Really, seriously, tough shit. He should have had the good grace to man up to Marr's questions rather than come across all X-Factor, whether it was real or not.
There are parents, brother, sisters, wives and husbands both here and in the Middle East who have shown a lot more humility and diginity regarding their own part in the war. Campbell should remember that next time he decides to share his pain on the part he played in taking the country illegally to war.