How can i prevent myself from being ripped off? -

i am acting as a broker for a deal taking place in uk. My customer is willing to trust me with ��250k. I have to go to my supplier and buy the goods on my customers behalf.So, i have a signed and dated purchase order from my customer. I am going to send a purchase order to my supplier, with the condition that my customer is happy to buy the goods and sends the money (he will view the goods before he sends the money to us). I will then require a proforma invoice from the supplier.The goods are brand new and in unopened boxes....so i cant check them all because they are unopened.....plus there are 10 truck loads. So i have to assume that a few random spot checks are ok. But how do i know that the supplier will release the goods once i pay him? I presume that if challenged they would have to produce a shipping manifest saying the goods were sent....the customer is arranging the transport....i am not too worried about the customer/supplier meeting... too long to explain.so, im wondering what else can go wrong, and how to cover my back side.ps, the supplier is reputable....but still, to me its a hell of a lot of money and even a tiny bit of trust is a LOT!!!thanks for answers

use a bonded warehouse to hold the goods till they are paid for. ASK an atty to set it up