I was just wondering if someone can speculate the time difference between UK and US market... For ex. in UK the BP.L (stock) is trading at 0.78% down from yesterday, and in US in premarket is about 0.1% down, so it makes sense to short some more...no?
I don't know about your strategy above, but occasional arbitrage does occur (albeit with some execution risk)... When both the UK stock and the ADR is trading, assess the $ and £ bid/ask spreads... apply brokerage currency conversions to each of the 4 numbers and if there is a post-commission discrepancy after currency conversion, try and lock in the spread discrepancy...