Chartman
the gap(s) are a puzzle, especially as we see so many.
as a working hypthesis, I put it down to the weightings of the
majors which can swamp the index calculations.
so, theoretically and as an extreme example, a major sweep through the order book causing a 5p move in VOD would cause a gap in the index the instant the transaction(s) was effected.
from memory, FTSE is recalculated every 10 seconds (?), so
for this to coincide with the end of a 1 min bar or 5 min bar
would be nothing short miraculous!
so something else is going on as well.
It may often have something to do with the LSE data feeds.
any suggestions/thoughts would be welcome.