Good Luck to him - They’ve been trying to find drivers since August, if not before. It’s very physical work.
It’s drinks deliveries to pubs and nightclubs - Including taking the drinks down to the cellars etc.
Because they had a lack of staff, the schedules are nigh on impossible. The contract might say 48 hours but in reality it might be more like 55 hours.
Some drivers load their own trucks in the morning due to the lack of staff.
A colleague from a previous job did a day there - he only did the 1 day and this was back in August - Maybe things have improved since then. 
Short of being found guilty of murdering someone - They will almost certainly offer him the job.
If your mate enjoys charades, he’ll get on with the driver’s mates great 
I believe that DHL site take on new passes for Class 1 and 2
I’ve not worked at that DHL site but I have at others. I would recommend keeping a diary or something of the hours worked to make sure the pay slip is correct.
If he might be interested in overtime (If that site does that) Find out the terms of pay. One DHL site I know pays overtime quarterly 