With £20,000 coming to the table today Show 677 it makes it the second occasion this has happened, the other time being Shows 324-326. £1,000 came to the table in 3 consecutive shows also - Shows 477-479.

I know it's not a box amount but box 9 also came to the table 3 times in a row in December 2006 - Ingerlise, Ned and Maggie(?).

A 1 in 10648 chance of 3 identical values/boxes coming to the table I make it?

Yep, it's the chance of the same amount being on the table in 3 specific shows.

£20,000 came to the table three times before December 2006 (Lynsey/Gary/Jim)

That's the chance of a specific value appearing on the table in three specific games. Since we're not especially interested in the fact that it was specifically £20k and we'd have been remarking on the occurrence of any value appearing three games running, the relevant probability is 1 in 484.

Also, since we've had nigh on 700 games now, it's really not that unusual for a 1 in 484 chance to have happened once or twice in that time...