LSE shuts down trading for affected instruments

" Thursday, 19/10/2023 17:05:58 FTSE 100, FTSE 250 and IOB securities closed as normal.

London Stock Exchange has invoked a Halt & Close for affected instruments. A closing price for the affected securities has been set and disseminated."

How often has something like this happened in the past? Are we talking like a rare occurrences for a couple years or like a really rare occurrence?

Paste from a now-buried supa post...

"I asked Chat GPT to dumb this down. Here’s the following explanation:

“Here is a simplified version of the statement that a high school student might understand:

The London Stock Exchange is a place where people can buy and sell shares of different companies. Sometimes, people want to buy or sell a lot of shares at once, so they ask for a special price from other traders. This is called Request For Quote (RFQ). RFQ is only available for some types of shares, such as Exchange Traded Products (ETPs), which are like baskets of different shares.

On Thursday, October 19, something went wrong with the RFQ system for ETPs. It caused some of the shares to stop trading for a while. This did not affect the most popular shares, such as the ones in the FTSE 100 and FTSE 250 lists, or the ones from other countries. The problem was fixed by deleting all the orders that were not completed and restarting the system. However, it was too late to do the normal closing process for the affected shares, so the closing prices were based on the last trades that happened before the problem.

On Friday, October 20, everything was back to normal, except for the RFQ system for ETPs. It was turned off until they figure out what caused the problem and how to prevent it from happening again. They will let everyone know when it is safe to use it again.

Source: Conversation with Bing, 10/20/2023 (1) Request for quote - Wikipedia. https://en.wikipedia.org/wiki/Request_for_quote. (2) . https://bing.com/search?q=what+is+RFQ+functionality+for+Exchange+Traded+Products. (3) Request for Quote (RFQ) - CME Group. https://www.cmegroup.com/education/request-for-quote.html. (4) Request for quote in equities: Under the hood - The TRADE. https://www.thetradenews.com/request-quote-equities-hood/. (5) Exchange-Traded Fund Trading RFQ - Business Insider. https://www.businessinsider.com/exchange-traded-fund-trading-rfq-2017-1. (6) undefined. http://www2.lseg.com/rfq2.0.”