‘’Lo, Auntie Tilly,’ he says without diverting his eyes from the screen. ‘I’m watching Thomas.’

‘So much for his excitement,’ I tell her with a laugh.

‘Be polite, Isaac,’ Tash warns him, reaching for the remote and pausing the action.

Isaac rolls over with a sigh to attempt the greeting again, but his eyes widen when he catches sight of Will.

‘Who are you?’ he asks.

‘This is my friend Will,’ I explain. ‘He’s coming with us today.’

Isaac stares at Will without speaking as he digests this new information.

‘I’m very pleased to meet you, Isaac,’ Will says, settling himself down so he’s cross-legged on the floor next to him. ‘Your Auntie Tilly has told me a lot about you.’

This is enough to disarm Isaac, who is obviously delighted to think that he’s been the centre of attention without even needing to be present.

‘I was watching Thomas before Mummy stopped it,’ Isaac tells him, shooting Tash a resentful look. ‘Do you know Thomas?’

‘I do.’

‘Who’s your favourite?’

Tash and I hold our breath as Will considers. This is a make-or-break moment. If it turns out he doesn’t actually know anything about the programme, Isaac won’t be impressed.

‘Percy, I think,’ Will says eventually.

Isaac laughs dismissively. ‘But he’s just a little engine,’ he scoffs. ‘Gordon’s the biggest and fastest.’

‘Yes, but Gordon was built to be big and fast, wasn’t he?’ Will counters. ‘Plus, he’s not always very nice. Percy may be little but he always tries hard, and that’s more important than just being good at what you were made to do, I think.’

Isaac is patently unused to having his views on the subject challenged, and stares at Will open-mouthed. Will may have passed the knowing-what-he’s-talking-about test, but Isaac isn’t really old enough to be good at accepting different points of view yet.

‘I suppose Percy’s OK,’ Isaac says eventually.

‘And Gordon is pretty cool too,’ Will offers, which obviously pleases him.

‘Do you want to finish the episode before we go?’ I ask Isaac.

‘Only if Will watches with me,’ he replies firmly.

‘Of course. I’d like that very much,’ Will tells him, earning himself a beam from Isaac in return.

‘I’ll stick the kettle on then, shall I?’ Tash suggests. ‘Tea or coffee, Will?’

‘Tea, please,’ he replies as she presses the button and the action starts again. ‘White with no sugar if that’s OK.’

‘Squash,’ Isaac adds.

‘Squash…?’

‘Squash please, Mummy.’

‘Yes, your lordship. You can come and help, Tills.’ She takes my hand and practically drags me out to the kitchen while Isaac begins to explain what’s happening on-screen to Will.

‘Where the hell have you been hiding him?’ she demands as soon as she’s sure we can’t be overheard. ‘He’s gorgeous, and his eyes! They’re contact lenses, right?’

‘No. His father’s are the same.’