Why have MPs from the SNP decided to block plans to allow shops in England to open for longer on a Sunday?
It's an intriguing question - more so when you consider the fact that shops in Scotland can already open for as long as they like.
The SNP has previously said that its MPs would not interfere in matters which only affect England (or England and Wales).
But tomorrow the nationalist MPs will join Labour MPs in opposing the deregulation of Sunday trading in England and Wales.
Their votes are crucial because 25 Tory rebels have already said they oppose the move. It means the decision by the SNP tonight effectively kills off the government's plans.
Currently, large stores in England and Wales are restricted to six hours of trading on a Sunday, and usually open from either 10am to 4pm or 11am to 5pm.
The SNP says the decision was not made to make life difficult for shoppers in England, but to protect the pay of retail workers in Scotland.
Shop staff currently get a premium for working on a Sunday but the SNP - and unions like Usdaw - believe an extension to Sunday shopping hours in England and Wales would increase the likelihood that retailers would pay just single time for staff across the whole of the UK.
So, unless there is a set of changes from government it seems Scottish MPs have prevented English shoppers from doing what Scottish shoppers can already do.
On Sunday, you could read about it in a newspaper purchased from a 24-hour supermarket in Scotland.
But in England you would have to wait until 10am to purchase the newspaper from a similar-sized store.