The disturbing case of the missing NIR

Telegrammed by 221b Baker Street
'I say, Holmes, what do you make of the disturbing case of the Pacer engine, found near Olive Mount junction?

'Watson, you will of course have noted the significance of RAIB's investigation and the detail of the event contained in the NIR.'

'But Holmes, RAIB is not investigating and there has been no NIR!'

'That, Watson, is the significance!'

UPDATE: The NIR has apparently now been published and RAIB are involved!