Tickets for that weekend aren't even available to purchase on the Eurostar website - even though all other dates including most later weekends are on sale.

I'm guessing it's trackwork, and the timetable isn't finalised yet. It won't be sold out. I would check again nearer the date. It's possible that no trains will run because of track works.

Longer term, trains to Amsterdam might be completely suspended for a year while construction work happens at Amsterdam Centraal, but I don't think that's scheduled until later in 2024.

You could also keep an eye on the Eurostar travel disruption page. Although there's nothing there for 20 April

https://www.eurostar.com/uk-en/travel-info/travel-updates

Ok noted. Thanks for your prompt reply.

Yes I also checked the Eurostar website and 20th and 21st, both days, the calender is still not opened to book.

So shall I wait for the updated calender which is due in December( read in some other conversation link) or shall I go ahead and book London- Bruxelles midi train and then IC train to Amsterdam Central?  Ofcourse this is a non direct train that would be complete waste of time as I was looking of direct link.

But don't know what to do, as my Europe tour from London- Amsterdam- Paris- Interlaken- Florence- Rome, all bnbs have been booked and flight to and fro already done.

Your advice would be appreciated.

Changing to the IC at Brussels would cost you an hour or so Vs the direct train.

If it was me, I’d wait a little longer to see if the Amsterdam train opens up, or you find any news that they're not running that weekend. But keep an eye on availability to Brussels. If availability starts to dry up, that's a sure sign to get it booked ASAP.

Is there no way you could change your plans and travel on the Friday?

Yes, your advice seems good. Will wait for few weeks, checking the schedule of this particular train as well checking updates for disruption. 

Also, will keep a check on the Brussels availability. 

In the meantime, will try to see if the our travel schedule can be adjusted to book for 19th April instead of 20th. 

Thanks for sharing your advice.

One more query, if I going for change over at Brussels, ,do I have to reserve seats for IC train from Brussels to Amsterdam Central like I did for Eurostar? Or buy train tickets online in advance or at the station itself? 

Thanks in advance

No, on the IC you just hop on. No reservation needed.

You would need a reservation if you take the Eurostar (the high speed trains formerly known as Thalys, but now confusingly called Eurostar!).

Oh, gosh, how do I find out about this suspension as we will be traveling from London to Amsterdam early September  

https://www.euronews.com/travel/2023/06/05/eurostars-london-amsterdam-trains-to-be-suspended-for-almost-a-year-from-2024

There's still no final decision on that, although it should be there soon.