What is this type of valve called?

[Rollerball]

The valve below is part of the cold water feed that goes to the small storage tank in my attic - this tank contains the water for the central heating. When I turn on the valve it leaks a lot so I currently have no central heating.

What is the valve called, and if I can't get one what can it be replaced with?

 

[just pumps]

Isolation valve.

 

[Rollerball]

Thank you.

 

[Dan Robinson]

Isolation valve.

You forgot to put "Crap" at the beginning

 

[just pumps]

They all hate me
I look at one
And it starts leaking

 

[Dan Robinson]

I refuse on general principle to touch one unless it's coming out.

 

[oilboffin]

Shocking things I hate em can't beat a good old full bore lever cock.Bob

 

[dilalio]

@Rollerball replace it with one of these...

https://www.screwfix.com/p/pegler-ball-valve-blue-15mm/11085

 

[Rollerball]

Will do, thanks!