Header missing and I'm clueless

Site URL: https://www.bost.org.uk/marlborough-sports-garden

Hello, I had to add an iFrame to a page on our website, which worked and thanks to a post here i even managed to set the height and width and felt quite proud of myself.

HOWEVER, today I've noticed that the header and footer have now disappeared from that page so a user can't navigate out of it! Disaster! I checked the embed code I added for the iFrame and I can see that it would delete the header/footer and the settings for the page look no different from other pages like it on the site. I have no idea how to restore the header/footer - any advice welcome. 

This is the embed code I used: <iframe src="https://banksideopenspacestrust.bookteq.com/api/hosted-widget/f92610bf-79bf-4932-94be-da23061ab712" width="100%" height="783" style="border:medium solid rgb(0,0,0)"

This was the only change I made to the page so I guess it must be connected.... 

I am totally unskilled at all this btw. Can you tell? 

Also I just tested out deleting the iframe and seeing if the header/footer came back and it did... Do I need a dd something to the imbed code perhaps

Thanks - good to know.