the way I read it is that the ASX and LSE are contractually...

the way I read it is that the ASX and LSE are contractually linked via a CDI agreement and therefore if the ASX holds a current valid sell contract (even after hours) for PM8 a LSE buyer can buy it. The LSE will fulfil the PRE.LSE contract either with the lowest price between the LSE and the ASX/Frankfurt CDIs (which will then be converted to shares in PRE on the LSE). By this arrangement the CDIs should quickly reflect the LSE PRE SP otherwise LSE buyers will buy CDIs on the ASX and sell them as converted shares at a big profit on the LSE. I wouldn't trade this share/CDI unless you never sleep.