I have to dispute your statement, T4tomo.
Several years ago, might have been around 2011/2012 I bought a Samsung TV from John Lewis. Shortly after that I discovered the same model was available at a large national retailer. I submitted a claim to JL and very promptly received a refund of approx £40. The very same thing happened after I had a fridge/freezer from JL and once again my claim was honoured and I received a refund of the difference in price.
Having their “Never knowingly undersold” policy in place plus the fact their guarantees were often longer than other retailers was the reason that my major household purchases were obtained from John Lewis.
I fear that John Lewis’ golden days of best price and best customer service are fast disappearing.