Alice and Bob live in London, UK. On a Friday, as per usual, Bob leaves for work before Alice. At lunchtime he receives a WhatsApp message from his friend Charles:
Sorry to cancel on you last week (hope you weren’t too BORED without us!). Rest assured, Denise and I are on for tonight, so we’ll be round at eight as usual. See you then.
This news puts a spring in Bob’s step for the rest of the day, and when he gets home in the evening to find a pad of paper on the kitchen worktop with a note from Alice pointing out some housework that needs doing before their guests arrive, Bob doesn’t complain. As requested, Bob empties the dishwasher and puts the hoover round. Then he spots a shopping list that had been lying next to the pad. At first glance something strikes him as oddly familiar, but he can’t put his finger on it. Shaking it off, in his current helpful mood Bob pops out to the shops and promptly picks up all the items on the list.
When Bob gets home he finds Alice in the kitchen and holds his bags of shopping aloft with pride. She looks up at him with a quizzical expression.
“I’ve done the shopping!” Bob states proudly. “I found your list and thought I’d pop out and get it all for you.”
Alice looks completely bemused. “My list? I never wrote a list – just that note about those chores for you. Then I went straight back out to the supermarket to get what we need for the weekend, just working off the mental list I keep in my head.” Alice gestures to some other shopping bags she was already in the middle of unpacking when Bob arrived.
“Oh,” says Bob, confused. “Well, er... I found a list on the worktop... I wasn’t entirely sure about it, truth be told – there was a lot of alcohol on it for one thing, but I assumed it must all be ingredients for a dish you were going to make or something...”
Alice still seems bewildered, but then something strikes her and she laughs suddenly.
“Oh Bob! Show me the list…” Bob hands it to her. Alice laughs and laughs and laughs. Wiping tears from her eyes, she puts a hand on her husband’s shoulder. “This is most definitely not a shopping list – and I don’t know how you’ve forgotten what it actually is, especially seeing how you've been crowing about it all week!”
What does this list (pictured below) represent? What has Bob been ‘crowing about all week’? A complete solution requires a fully correct diagram to be drawn, explaining how this list came to be...
NB I believe that – symmetry aside – there is a unique solution to this puzzle. However, I am happy to be corrected and will consider alternative solutions if they can demonstrably be proved to work! I advise against posting partial solutions without the diagram – answering the initial questions may be relatively simple for some puzzlers, but constructing the diagram is potentially the most difficult and labour-intensive part of the puzzle.
Post-script: As Deusovi demonstrated in his excellent (and very well explained) solution, there is an alternative valid diagram to the one I initially intended. The overarching solution to the puzzle is unaffected (phew!), but I am happy to concede (re the assertion of uniqueness in the paragraph above) that I stand corrected!