Morning all. I'm after some advice regarding running power out to a new man cave that is soon due to land. The run from my existing CU/incoming mains to the new CU that will go in the cabin is 20 meters. I intend to run a small ring (1 x 32A), lighting (1 x 6A) and provision for a hot tub that will be external to the cabin (so 1 x 32A to feed a rotary isolator). So max current pull is 70A As a bit of background. My dad is a retired sparky. Spent his life in a prison doing electrics. On the right side of the bars I hasten to add. The bottom line is everything he does has to be 110% safe. By his own admission he is out of touch with what 18th edition may mean and wanted me to try to get confirmation before we go and buy anything. He has suggested splitting the incoming tails into a Henley block and running a 2 way board with an RCD in it at the head end (simply because they are much cheaper than a fused switch). This connection will obviously be done by an electrician. I would then feed out to the shed (see question below on cable), all of which is above ground clipped to a fence. This will run into a 4 way board in the cabin with RCBO's. My questions.... 1 - Is the head end connection OK? I am assuming it will need to run into a compliant small metal CU. 2 - I've used an online calculator (Doncaster cables site) and it is confirming 16mm SWA. It also shows 10mm Tuff Sheath as an option. Would this be OK? I planned to use 3 core with one core exporting the earth (TNCS earth on incoming). I used 5% for the volt drop calc. 3 - Is exporting the earth OK? My dad seemed to think a 20M run on 10mm or 16mm would be OK but was not sure on the regs with one of the RCBO's being for a hot tub. Or do I now end to rod it at the cabin and provision the earth here? 4 - Probably the most contentious one. As my old man is more than competent I was intending to get him to do most of it with the exception of the connection of the tails in to the new switch. If everything is left exposed/open for inspection and test would most sparkies be happy to certify it when they do the connection? Many thanks in advance for any help or advice and apologies for a very long winded post. I just wanted to put as much info in as possible.