This is what happened29 May 2026 18:18
Here is a small summary of why the big trades at the end of the day:
The massive, multi-million-share buy orders that finally flooded the tape at the 4:30 PM closing bell happened for one strict reason: forced, rule-based index replication by passive asset managers
1. The Mandatory MSCI Rulebook
Today, Friday 29 May, is the official effective date for ITM Power’s inclusion into the MSCI United Kingdom Small Cap Index [69416940].
Passive index-tracking funds managed by giants like BlackRock (iShares) and Vanguard are contractually and legally bound to mirror this index exactly.
If the index adds ITM Power, these tracker funds must buy the shares to match its exact weight in the index. They have no choice, no human input, and no opinion on the stock price.
2. The Hunt for "Zero Tracking Error"
You might wonder why these funds didn't just buy the shares earlier in the week when it was cheaper.
If a passive fund buys a stock even one day before the official index change, its fund performance will drift away from the index benchmark (known as "tracking error").
To eliminate this risk, the funds program their automated algorithms to execute the entire multi-million-share purchase at the exact second the market closes on the effective date. This ensures they pay the exact official closing price of the day.
3. Sourcing the Hidden Liquidity
Because the available pool of ITM Power shares is highly restricted (with the UK Government and Linde plc holding large chunks locked away), the tracker funds could not buy 15 to 21 million shares on the open retail market without crashing the system.
To prevent a total market blowout, these massive orders are saved for the 5-minute Closing Auction.
Active hedge funds, who had spent the last two weeks accumulating shares lower down, stepped forward at 4:30 PM to dump their blocks onto the other side of the ledger.
The computers matched the forced buyers (Vanguard/BlackRock) directly with the profit-taking sellers (Hedge Funds) all at once, creating that massive, spectacular block trade print..
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