All applicants and holders of lorry and bus licences are subject to more severe conduct requirements than ordinary licence holders.
When applying for lorry entitlement, you should disclose cautions, convictions and fixed penalties relating to vehicle road worthiness, loading or drivers hours (More information about drivers hours can be found here).
If you are applying for minibus or bus entitlement, you should disclose any unspent cautions or convictions.
The relevant section on the D2 Application for lorry, bus or minibus driving licence ask:-
The Secretary of State for Transport may refer any case where a question arises relating to the conduct of a lorry or bus driver to the Traffic Commissioner for the area in which you live. In all cases the Traffic Commissioner, acting on behalf of the Secretary of State, will decide whether or not to grant you entitlement to drive a lorry, bus or minibus.
The government have released an information booklet that provides assistance with filling out your application form for a lorry, bus or minibus driving licence (INF2D). For further information please read the following leaflet (page 8).