These cars were powered by the 1292cc MPJG engine.
As Colin says, the Craigantlet car was TA0930 (ABL 960).
The 1938 Works supported 'Cream Cracker' TAs were:
BBL 78 (TA2017) Toulmin (Car number EX155/2) BBL 79 (TA2018) Crawford (Car number EX155/3) BBL 80 (TA2019) Jones (Car number EX155/4)
There was also BBL 81 (TA2020) Imhof (Car number EX155/5)but I don't think he was a team member.
The 1938 cars were originally fitted with 1548cc VA engines but these were bored out to 1708cc using WA 73mm pistons by March '38.
The EX/ numbers are shown in the Production records in a separate column alongside the chassis numbers. Also listed in this column are details such as 'EXP' (export) CKD (completely knocked down) and a couple of entries which read 'Show Car'.
Following on from the photo of Maurice Toulmin in 1935 above, the results show that, as well as competing in the unsupercharged classes he came 3rd in Class 5 - Racing and Supercharged Cars - with apparently the same car and a contemporary report says "Toulmin's efforts at supercharging his MG proved a failure as the car was considerably slower".
Can anyone confirm this as it seems to be quite a challenge to change from carbs to a blower between runs in different classes?
I think you could do the change of an under bonnet set up in an hour or so, but getting it to run properly is evidently another matter!
According to Roger Thomas' book 'MG Trials Cars' Toulmin took 3 class wins at this event.
Regarding the Altette fitting, it may have been regulation, I can't see any other reason for leaving it on - if you can't hear a MMM car approaching you probably won't hear the horn!
You could well be right about the horn, Graham, as it was certainly the practice some years ago for the cars to freewheel silently back down the hill for their next run and in such circumstances a horn might be useful to warn straying spectators.