is this a legitimate cgt tactic, page-2

My opinion only

Any "wash" transaction that is clearly designed to minimise CGT obligations is a no-no. Having said that I would suggest that 99% of punters (me included) do such transactions.

The more obvious you make the exercise, then the less chance you would have in arguing your case - if in fact you ever got picked-up.

At one end of the scale would be a buy/sell or sell/buy trade for exact parcels, executed within seconds of each other.

On the other side of the scale, (a) if you were a regular punter (b) already held 200.000 of the stock (c) bought a couple more parcels totalling around 200.000 in the morning and then (d) sold off 200.000 later in the day (or next), then you may have good case.

That is, you are familiar with the stock and decided to "double up" on a punt. After several hours, or a day, you decided you "got it wrong" and cut your holding back to the original stake.