@Melroses
Who/What is the function of "Leading Counsel"
In complex cases or cases if significant interest, leading counsel is the barrister heading up a team. They will almost always be a QC of senior standing and a specialist in the field. They will (usually) travel all over and take cases that are of particular interest or importance. Other junior counsel will work below them, although "junior" can still mean very experienced people, just not QC titled.
Leading counsel can be appointed from within your own chambers if you have a suitable senior counsel or from other chambers of not.