can you still pull it if the disc has fell out the holder and it’s lost?
technically yes as it is still MoT’d, but there may be an offence of failing to display, the same as road fund licence disc
i’m sure someone will be along shortly to either confirm or deny 
But as a driver,how would you know if it’s got an MOT?
I once refused to pull a trailer for the same reason,and I was assured that it was tested,but I stuck to my guns,and the company I was working for,had to go and hire another trailer.
As part of your checks,you will have a box to tick to say that the trailer has an MOT disc and if one isn’t visible,you would be well within your rights to refuse to take it,unless the company can prove it is tested.
Ken.
I picked up a tesco trailer and questioned the mot disc, their own transport manager said if it’s not displayed then it’s not going out. It was a brand new trailer and therefore doesn’t need one. Could tell it was new but how would you know that in 3 months time when some ‘not me’ drivers have had their hands on it.
Rick B:
Could tell it was new but how would you know that in 3 months time when some ‘not me’ drivers have had their hands on it.
By checking the manufacturing date on the metal VIN-type plate 
I once picked up a trailer, which had just been brought in by A.N. Other driver, with no axle-weight cert on it. The nightshift TM was on holiday and the two space cadets left in charge didn’t have a clue. I refused to take it and it had to be transhipped. The shunter had a go at me and accused me of being ‘jobsworth’, as according to him, ‘there was nothing wrong with the trailer.’ And there was a major bust-up between me, my boss, (who was behind me 100%) and the customer.
When all’s said and done…it’s my licence at risk…not the two space cadet’s nor the shunter’s.
it could be handy to take a copy of the mot certificate with you VTG5 i think