Illegal double or mechanical error?
The bidding went 1H - No - No - X - No - No - considerable pause then X. All three other pairs expressed surprise in some way and the second doubler looked at his bidding cards and said immediately “sorry, mechanical error, I meant to redouble”. Is he allow to make the substitution?
It seems to me that there are two possibilities:
1) the second doubler thought the previous double was something else and intended to double. In which case the substitution is not allowed.
2) the second doubler intended to redouble but was away with the fairies and pulled out the wrong card. In which case, assuming it was agreed the error mistake was pointed out immediately, the substitution should be allowed.
Are there any subtle points I am missing?