Video by the British Museum
For the recipe, click here.
I love the string technique...
In the video, the baker says he's using buckwheat flour as the Romans did in those days but the list of ingredients in the posted recipe calls for equal amounts of spelt and whole wheat flour. Note that the bread is shaped right after mixing and that there is only one fermentation. Not a very long one at that, most likely because of the very large amount of starter and the use of wholegrain flours. No mention of steam to promote oven spring, probably because the bread found during the excavations looks quite flat. If you make the recipe at home, remember that the posted baking temperature (200°) is expressed in Celsius: it translates into 392°F.
The recipe lists gluten as an ingredient, which I find slightly odd. I can't imagine the Romans being in a position to supplement weak flour with gluten flour although, according to this article (scroll down to the paragraph titled Grains in Rome), they did favor high-gluten wheat. So maybe the added gluten is today's baker's way to approximate the wheat variety used in the original recipe.
For more info on ancient Rome's access to grain, you may want to read Grain Supply to the city of Rome on Wikipedia.
Too bad the British Museum doesn't provide a crumb shot. I would have loved to see one. My guess is that the bread turned out rather dense.
What makes my head spin is the idea that a bread could stay in an oven for close to 2000 years...