They are en route as I type, part way through a 250 mile journey to surprise DS for his birthday. The plan was they would be here to meet him off the bus, which gets here in about an hour. Currently they are an hour and 15 minutes away 
I'm not surprised, they have form for this and in all other ways are devoted if slightly indulgent GPs. I just despair of their appalling lack of urgency. They have text me three times so far to let me know they have stopped for "a cup of tea"
And I do appreciate them making the journey, I know it's a First World Problem etc. but this was supposed to be a surprise for DS. At almost 10 I am most unlikely to pull off a convincing enough excuse for the guest beds being made up and the suspicious tidiness of the house 
I normally stipulate a time at least an hour before their presence is important but sadly cannot swing a bus full of children being parked in a lay-by until they meander into view 