The London Stock Exchange is experiencing technical problems and has halted trading on all UK equity markets.
At 8.03am the exchange put trading into pause mode and then halted it at 8.30am.
A spokesperson at the company says it is investigating the problem, but added that the issues were related to market data.
The London Stock Exchange's latest update to the problem says: "[We] continue to investigate the market data issue. Participants can continue to delete but not enter orders at this time and no automatic execution is taking place."
The stock exchange migrated to its new core trading platform, MillenniumIT, on 2 February this year.