Just a short note to say that the last couple of posts were written before I had the replies that appear immediately before it.
Thanks to the replies I have now decided that what I was proposing will not work. Which means there is no harm in sharing what I was investigating:
When you take a spreadbet on cable they give you a pound for every .0001 change. This is not quite the same as buying dollars and then changing them back and it was this difference I was thinking about arbitraging.
For example if GBPUSD is at 1.5, imagine that I bought one spreadbet and at the same time exchanged £15,000 into $22,500. If the exchange rate fell to 1.0 then the spreadbet would lose £5,000, but the hard cash would be worth £22,500 - a gain of £7,500 and I would have a net profit of £2,500.
If cable had risen to 2.0 then my spreadbet would have made £5,000 and my hard cash would be worth £11,250 - an overall profit of £1,250.
The secret to success regardless of the movement to cable is to exchange in hard cash exactly the same amount as the notional value of the spreadbet.
Obviously I wouldn't get rich very quickly if I was waiting for cable to rise to 2.0 or fall to 1.0 so with a bit of maths and a spreadsheet I calculated the following:
cable £ $ contracts
1.6013 2,497,999 4,000,000 156
1.5962 2,505,993 4,000,000 157
1.5911 2,513,961 4,000,000 158
1.5861 2,521,904 4,000,000 159
1.5811 2,529,822 4,000,000 160
all I had to do was buy $4m and take out the appropriate number of spreadbet contracts. Then whenever the exchange rate hit one of the values on the left, buy or sell a spreadbet contract to balance things up.
To save you doing the maths my overall balance would increase by £25 whenever there was a .005 change in the exchange rate. This happens on average 2.75 times a day and so the scheme would bring in on average £68.75 a day.
You could also add to this the fact that the spreadbet company will pay you for being long in GBPUSD, which for 158 contracts is about £94.80 so the only challenge is to find out where one can buy $4m dollars for less than £150 a day, hopefully a lot less.
As I have now found that is basically impossible and the scheme is a non-starter - so it is back to my existing scheme "Suicide Trading" - until the next idea.