None of the major players in the Irish supermarket sector, bar the Musgrave Group, discloses any meaningful financial information. Dunnes Stores avails of a complex structure involving unlimited companies to keep its figures confidential, while Tesco, Aldi and Lidl all roll their Irish operations up into their UK businesses, which serves to muddy the waters.

In the case of Aldi the Irish numbers are consolidated into the accounts of Warwickshire-based Aldi Stores Ltd, which recently filed accounts for 2013. Some light is shed on the profitability of the Irish business by the annual tax charge, which came to £61 million for the year and included a figure for £11.2 million in respect of overseas tax.

Given that the only other country in which the group appears to operate is Ireland, it's reasonable to assume that this is Irish corporation tax of almost €13 million at today's rates. On the basis of the 12.5 per cent rate this would imply profits of almost €100 million. Not bad given that profit for the whole group was £261 million.

Assuming margins are the same in both markets at 5 per cent , this in turn implies sales of almost €2 billion in Ireland. This however does not chime with Aldi’s 8.3 per cent share of the €9 billion Irish grocery market, which suggests sales of about €1 billion.

There are two possible explanations. One is that this back- of-the-envelope calculation has gone an assumption too far. The other is that Aldi’s margins in Ireland are double the group average. That would certainly explain all the secrecy.