A method of operating a communications device in a wireless communications system that supports a random access procedure. The method comprises receiving, from an infrastructure equipment, a scheduling message comprising an indication of an allocation of radio resources to be used for a random access procedure message, selecting a transport block size (TBS) from a plurality of permitted TBS values for the transmission of the random access procedure message, and determining whether the selected TBS is lower than a maximum TBS of the plurality of permitted TBS values. If it is determined that the selected TBS is lower than the maximum TBS, the method comprises selecting a time for starting the transmission of the random access procedure message from a plurality of permitted starting transmission times, and transmitting the random access procedure message to the infrastructure equipment in the allocated communications resources using the selected TBS.