OK, so here I am again to report my experiences transporting 150oz in silver rounds and 3oz in gold coins from London UK to Melbourne Australia.
The reason my account name is different is that I could not remember my password and used a fake e-mail address to register first time around (and this time

)).
In the end I ended up booking my flights with Thai airways travelling via Bangkok Suvarnabhumi airport.
My itinerary was as follows: I was travelling from London Heathrow for 11 hours to Thailand, with a 2 hour stopover in Bangkok, and then another 9 hour flight from Bangkok to Melbourne.
I retrieved my coins from secure storage several days before my flight and began to formulate a "carry-plan" - the coins were stored in a metal lock box - and I decided to ditch that for the flight.
The reason was it was simply too heavy, and the coins were heavy enough. Also, I thought a huge metal box in a backpack would raise eyebrows for sure when passing airport security.
I ended up transporting the coins in my toiletries bag of all places.
I noticed that my toiletries bag was quite large and could fit the coins comfortably, and had heavy stitching so I was confident it could take the weight without splitting, also, it has a nice heavy zip that opens up nice and wide quickly to display the contents to security if needed.
I removed my toiletries from the bag and put them in a plastic supermarket bag for the flight.
The first hurdle was getting from my accommodation to the airport.
I put the toiletries bag containing the coins in my wheelie case, leaving my backpack more or less empty, and used public transport to get to the airport (London Heathrow).
I then used a luggage repacking table at the airport to quickly transfer the toiletries bag from my wheelie case to my backpack.
I then checked in my wheelie case and obtained my boarding passes.
I then approached security.
I had decided beforehand to ask for a private screening, and approached the first person I saw in uniform. She said "why", and I just said back "valuable items" - and she said, fine, if the bag gets flagged by screening then you will be taken aside for a private screening.
So I got in line with everyone else, putting my backpack on the conveyor belt.
All my usual items (wallet, laptop, keys, etc) passed through OK, and the backpack was flagged for checking.
The guy on the other side of the scanner said, please wait and you'll be taken to a room for private screening, but there may be a wait.
I ended up waiting for about 15 minutes for another security person to arrive, which made me a little nervous because obviously you don't want to be standing anywhere around the security for too long, lest you draw attention to yourself, which is what I was trying to avoid at all costs.
The security officer carried the plastic tray with my bag and said come with me, there was a short walk to a room with a closing door.
He said wait a moment for another security officer, to act as a witness.
While I was waiting I noticed a clipboard on the table, and I could read the names of other people who had requested a private screening that day - it was about 11 AM, and there were already 4 or 5 names with the day's date.
So the "witness" arrived and the security inspection began - They opened my backpack and removed the toiletries bag.
Obviously it was quite heavy, and the security officer commented on that.
He then unzipped the bag and said, "what are these", to which I just replied, "silver coins".
He removed about half the coins and poked around the rest, then put all the coins back into the bag.
He then performed an explosives swab on the bag.
He made some comments about some new coin to commemorate Queen Elizabeth's 90th birthday, I just said, no I don't have that one.
Next I was signing my name on the clipboard, and then the security screening was over.
Took about 20 minutes all up with the wait.
The security area was not busy at all - just normal I think, not sure what would happen or how long it would take if the airport was busy or there were other issues, but I'm guessing it could potentially take a lot longer to get a private screening.
I was very early for my flight, but I felt somewhat relieved to have made it through the first security point OK.
I relaxed in the food area, having a coffee and a sandwich, and stocked up with some snacks for the flight.
All the while I was vigilant of my surroundings, discreetly keeping an eye out for anyone who might be keeping an eye on me, or busy areas, which I also avoided.
It came time to board the plane, and I placed my backpack containing the coins in the overhead storage for takeoff. The overhead was literally right above my head, and I was careful to monitor activity around it, I don't think anyone else put anything in there, the flight was about 1/2 to 2/3 full, and I had a row of seats to myself.
After takeoff I removed the backpack from the overhead and placed it at my feet.
The flight proceeded without problems, had a meal, watched a couple of movies and even went to the loo (rapidly) a couple of times, just leaving the backpack on the floor next to my seat. I did not take the backpack to the toilet with me, I thought that may arouse suspicion.
I discreetly checked the backpack a few times during the flight to make sure the toiletries bag was still present, all fine.
In Bangkok I disembarked the plane and was ushered through towards the departure area for connecting international flights.
There was another security checkpoint and I decided to use a different approach with the Thai guards.
I didn't request a private screening, and decided to just open the bag and display its contents quickly when the bag was flagged up for checking.
I thought the "private screening" thing might attract too much attention, and they might not even have the facilities or even know what I meant.
The backpack was flagged for checking as expected, and I just unzipped the toiletries bag quickly and said, "silver coins".
The security person just poked their finger around the bag, did an explosives swab, and then said "you go".
I rapidly repacked everything and made my way to the gate for the next flight.
Strangely, there was another security bag check before boarding, the security officer opened the toiletries bag and took a coin out and held it up for a second, then put it back in the bag, I just said, "coins". That seemed to suffice. No problems.
I made my way to the gate and boarded the plane.
Proceeded much the same as the first flight. I just kept the backpack as close to myself as I could through the whole flight.
I managed to stay awake through the whole thing which I think helped.
Arriving in Melbourne, I declared the coins, the inspector didn't even look at them. He just said "what is it", and I said just some gold and silver bullion I owned overseas I am now bringing to Australia. He just waved me through.
I had a ride organised for my arrival, so no more security issues from there on.
So the bottom line is, nothing to worry about really, just some common sense security precautions seemed to work fine for me, and no problems at all from immigration officers, security, or fellow passengers.