Carnet - that one again - entry into RSA sea port

[DevonSteveS]

We are doing some advance planning for our trip to Southern Africa. Our current plan is to container our truck (Land Cruiser) into Cape Town from the UK (UK registered truck/UK passport holders). From my recent investigations it seems perfectly possible to enter RSA by land WITHOUT using a Carnet (just pay for a TIP) but to enter RSA by port/container seems less clear (ie Carnet may be needed). I cannot find any definitive info - except that many believe a Carnet may be needed. I cannot understand why there should be any difference (except the standards/professionalism of Port staff) why it should make any difference what method the country is entered by. Potentially this is to do with first entry of SACU? Can anyone point me to definitive documentation and/or recent experience arriving at an RSA sea port. I don't want to get a Carnet unless it is absolutely necessary as it is not required elsewhere. I understand the pro's/con's of carnets/no carnets - any definitive information would be appreciated