Eigg quick mail service

The 67 inhabitants of a remote Scottish island are getting a better postal delivery service than the 7.5 million people living in London, according to a survey by guardian.co.uk.

More than 25m letters are stacked up at delivery centres following a series of regional disputes, according to the Communications Workers Union (CWU), although Royal Mail says the number is closer to 9m.

To see how customers have been affected by the recent strikes we posted letters every day for a week to addresses around Britain. Each letter was numbered so we could work out whether they were arriving in the right order, and whether any had gone missing.

Maggie Fyffe, who lives on the Hebridean island of Eigg, received each letter the next postal day after it was dropped in the letter box at our local post office in King's Cross.

According to Maggie the only day there was a gap was Wednesday: "The boat doesn't come over on Wednesday, but I got two letters on Thursday instead."

In contrast, those living in London have endured a very patchy service. Guardian.co.uk/money editor, Hilary Osborne, who lives in Harringay, north London, received the first letter on Tuesday – four working days after it was posted – then three all at once on Thursday.

She used a postcode calculator to work out that the Isle of Eigg is 554 miles (including a boat ride) from the King's Cross post office, while her home is just four miles away. She said: "It took six days for one of the letters to arrive. I can walk that distance in less than an hour!"

Another recipient who lives in Balham, south London, just 300 yards from the nearest sorting office, got the second letter to be posted on Monday. Letters three and four arrived on Tuesday, but there is still no sign of the first, fifth or sixth letters.

Post Office customers elsewhere in the country fared much better than Londoners. Paula Wheatland who lives in Cumnor Hill outside Oxford reported the arrival of her sixth and final letter on Thursday, with each previous one having arrived the day after it was posted. However, she added: "In the same delivery I got a card that was posted 12 days earlier."

Monica Insley (the writer's sister-in-law) who lives in Lincolnshire received all the letters the day after they were posted with the exception of the second, which has yet to be delivered.

Of the 111 letters we sent out 93 (84%) arrived the next day. This is short of Royal Mail's target to deliver 93% of first-class mail the next day. Nine of our letters are still missing in the system.

A Royal Mail spokesman said: "Royal Mail's first- and second-class quality of service in the most recent quarter exceeded their targets, with first class recording its best springtime performance ever, but we are clearly concerned that the CWU's localised action, mainly in London, is damaging service quality in the capital, and we again urge the union to abandon its totally unjustified strike action and get back to delivering our customers' mail."