‘How energetic are you feeling?’ she asked when they’d parked the car and wandered up Market Street. ‘Are you prepared for a climb?’

‘Bring it on,’ said Marnie cheerfully.

‘Well, I thought I might drag you up St Rule’s Tower. There’s such an amazing view from the top. It’ll give you an idea of the whole city and you can see for miles around, but you do have to flog up this steep spiral staircase with incredibly narrow stone steps – a hundred and fifty-one of them to be exact – and it’s even more lethal coming down. I think it’s worth it – if you feel up to it?’

‘Of course I’m up to it,’ said Marnie indignantly. ‘Why shouldn’t I be?’

‘Probably because you have this deceptive air of fragility and always look as if a puff of wind would blow you away,’ said Louisa, laughing. ‘Come on then.’

In the end it was Louisa, rather than Marnie, who got so out of breath she had to have a pause halfway up.

‘Are you okay?’ asked Marnie when they finally reached the top.

‘I’m fine.’ Louisa pulled a face. ‘I’d forgotten just how puffed one got and something seems to have gone wrong with my thermostat recently – or maybe it’s just the unpredictable nature of Scottish weather – and I seem to be permanently either too hot or too cold. I used to be a fitness fanatic but I’ve let myself go a bit lately and I’m out of training, that’s all. I shall have to take more exercise when I get back – start jogging or going to the gym again. It’s depressing how quickly you get unfit.’

‘Well you were certainly right about the view. It’s well worth the climb.’ Marnie gazed down. ‘It’s awesome. Who was St Rule anyway?’

‘Oh, some old monk who got a vision telling him to gather up St Andrew’s bones from the island of Patras and take them forthwith “to the ends of the earth” for safekeeping – or so legend has it. Imagine the inconvenience! It’s after lights-out, you’re tucked up in the dorm having drunk your medieval monastic equivalent of Horlicks and some bossy prefect of an angel goes and wakes you in the middle of the night to send you off on an errand like that! So poor old St Rule ups and goes to collect a kneecap, a tooth, an arm bone and a few fingers . . .’

‘As you would,’ said Marnie.

‘Exactly, as one would . . . and off he sets with them, leaving nice warm Greece and landing up getting shipwrecked on the bleak north-easterly shores of Scotland – and of course the bones were nicked a few centuries later anyway so he could have saved himself the trouble.’

‘This must have been a great place to be at college.’