British retailer Marks & Spencer has been in the headlines for all the wrong reasons after its operations were crippled by a cyber attack. Online sales have been suspended for over a month. The company says the incident will cost it around £300 million – a third of its annual profits.

I have an M&S Rewards credit card, which gives vouchers to spend online or in-store. I intended to buy a pair of joggers with the latest coupon, but had to go into a store to buy them given the website is now just a shop window. I did this at M&S’s flagship Oxford Street store in London yesterday. The sales assistant took one look at the paper voucher, and told me that she couldn’t accept it because of the systems failure.

I was astounded. I had presented a paper voucher clearly stating it was for £25, the price of the item. How could M&S be so reliant on an electronic point of sales system that it couldn’t accept a paper voucher? Way back in the 1980s, I worked in a Nationwide Building Society branch. If the system went down, we still served customers: we noted the transaction on paper ledgers, and reconciled them later. How could M&S not have a similar back up plan? How can it be forced to suspend online sales for over a month in an online era? Stressed out teenagers sitting their GCSEs are more resilient than this British retailing giant.

We shouldn’t be surprised. M&S was slow to embrace the online revolution 25 years ago, after waiting over 30 years before accepting credit cards (other than its own charge card) in its shops in April 2000.

The voucher I tried to use expires in just over a month. The manager at M&S Oxford Circus wrote a note on it saying it should be accepted for a further month. That was good customer service, but the highly paid executives at M&S HQ in Paddington, London, should be taking the heat, not the poor bloody infantry on the front line.