Bollotom
Ref RN swearing the oath of allegiance, see my post #107, which was correct. Your linked Wikipedia entry is out of date. This is from JSP 830, my bold:
8. Oath of allegiance. Whilst the signed declaration made at enlistment is a legal matter, the oath of allegiance has an educational, symbolic and solemn purpose. The swearing may be conducted during the first day of training or if considered more appropriate, at another suitable point, at the convenience of the single-Service. Swearing the oath of allegiance is a requirement of the Services for service in Her Majesty’s forces (this is a new provision for the RN because people offering to enter RN service have historically not sworn an oath of allegiance). Swearing the oath of allegiance is viewed as a mark of the individual’s loyalty to the Crown and therefore, their willingness faithfully to serve as a member of the armed forces.