Buy-and-build works commercially and fragments technically.
Every completed deal adds a stack the group did not design, integrations built under deadline, data structured for someone else's business, and owners who may already have left.
How the gaps form
A ledger feed, a customer sync, an identity link. The rest stays as it was: working, undocumented, unowned.
The spreadsheet emailed monthly to group finance was a Day-1 workaround. Three years on, it is the finance feed.
The engineer who understood the warehouse system retired. The integration still runs. Nobody knows what depends on it.
A diagram from the deal, a CMDB nobody updates, an integration platform that sees only its own flows, a monitoring tool per company.
Why the usual tools miss it
Integration platforms
See the flows built on them, not the file transfers, direct database links, emailed spreadsheets or the integrations on the other four platforms the group inherited.
Monitoring
Says a system is up. Does not say the feed between two systems is delivering 8% of the expected records, or that a field changed type upstream.
CMDBs and architecture repositories
Hold what someone typed in, on the day they typed it, with no way to tell verified from guessed and nothing reading the live estate to keep it true.
The transformation programme
Will fix it, eventually. Meanwhile the group keeps acquiring, and the board keeps asking whether the numbers can be trusted.
None of these is a technology failure
They are failures of visibility across the seams between systems. That is what a control plane is for.