The major grocery chains in Northern Ireland are The Co-operative Group, Iceland, Marks and Spencer, Sainsbury, Safeway and Tesco. Our mystery shoppers do not visit Iceland and M&S, so how do they measure up?

Iceland stores in NI are supplied from Scotland - on a six-day-a week delivery cycle from its Livingston depot says supply chain director Ian Keilty.

M&S uses ferries, mainly P&O, from Stranraer to Belfast. Stock is picked and travels from its national distribution centre in Cumbernauld in Scotland. A small depot at its clothing warehouse in Mullusk, Belfast, deals with locally produced food.been introducing similar stock checking initiatives to ensure that availability is high. And the multiple also reported its second full basket at Forestside in Belfast.

Sainsbury sources £150m of stock locally for delivery to its composite depot in Belfast. The remainder is despatched from mainland depots, primarily Langlands Park, near Glasgow. But like Tesco, Sainsbury has stumbled on fresh produce in visits by The Grocer 33 team of shoppers since June.

And it is intriguing that the distribution problems we have spotted have been as serious, if not worse, with locally sourced produce. This suggests that perhaps the Irish Sea may not be as much to blame for all the availability problems we have encountered.

All but two of the lines that have been out of stock in Safeway, for instance, are sourced locally. Fresh meat is the particular problem for the multiple. Aylwin expresses surprise. He says Safeway sources 20% of its lines locally - mainly product that is highly perishable - and another 20% is delivered by suppliers to its Larne depot. “In Northern Ireland we source locally through our Larne depot. If anything, I would expect stock levels would be higher than on the mainland.”

He adds: “Stock levels are not an area of complaint from our customers. We are hoping to return a full basket next time The Grocer 33 visits.”

But despite all the best efforts of the retailers, we keep on getting out of stocks. This week it was four in the Co-op we visited. Availability clearly remains something of a hot potato in Northern Ireland.