Morrisons caved. So did DHL. Eyes are now on Tesco to see if it will do the same. Britain’s biggest supermarket will certainly be feeling the heat after the public announcement that around 1,200 workers at four of its distribution centres are preparing to strike in the weeks before Christmas.

That’s not the end of it, either. The final ballots from a further nine Tesco distribution centres will arrive today to see if they will follow suit. If they do, workers at more than half of the supermarket’s distribution sites could soon be striking in the midst of the busiest month of the year.

In the face of such pressure, Morrisons granted a 5% rise for warehouse workers in November, and DHL gave drivers working for Sainsbury’s a 14% hike in the south west.

Tesco, by contrast, seems to be playing hardball. Andrew Woolfenden, UK distribution and fulfilment director, wrote to employees in October to warn they would be in breach of their employment contract if they opted to strike – a move Unite decried as “unlawful”.

In the letter seen by The Grocer, Woolfenden said striking would mean “1. You will not be paid for the entire shift(s) in which strike action is taken, even if you work for part of that shift.

“2. You may not be paid your colleague bonus for 2021. The average payment under that scheme last year was £801.

“3. You may lose your warehouse market supplement (up to £500) or driver market supplement (up to £800).

“4. In addition, if strike action continues for 12 weeks, we may decide to terminate your employment with the company as outlined in the ballot paper you will receive.”

Richard Thomas, a partner at Capital Law, believes Tesco “needs to be careful”. While it’s difficult to judge whether such claims are lawful without examining the specific contract, employees should not typically be disadvantaged for taking part in industrial action, he says.

Such a legal battle will play out if and when it needs to, but for now, all parties remain focused on the potentially imminent strike action. Tesco says its 4% pay offer is “one of the highest awards made within our distribution business in the last 25 years” and insists contingency plans are in place if the strikes do go ahead. Still, despite being “confident we will be able to fulfil our plans”, it will no doubt be wary of any potential disruption.

The unions know they are in a position of strength, with the labour market stretched at this most vital time of year. All supermarkets have struggled to recruit sufficient staff of late, and while supply chains are just about coping, they are fragile to further strain. Tesco will need some steel to tough this one out.