Can anyone identify this pre-War Ariel?

[Richard.Carrigan]

A chum has asked me to tell him which model his Father-In-Law is astride in this photograph.
My knowledge (I wouldn't call it expertise..) only goes as far as the Huntmaster, so could someone let me (him) know?
Many thanks in advance,
Richard

[Roger Gwynn]

Pretty sure it is a 1929 LF, which is a 250 ohv Colt. VB is a London number issued between June 1927 and May 1930.

[Karol Burger]

Roger proves once again that he is one of the building blocks of this club. You are an inexhaustible reservoir of information. Thank you for your help.

[Richard.Carrigan]

Many thanks Roger!