Have found this:
"when working with two assistants, may care for no more than 6 children under 8 years; of these, not more than 6 may be in the early years age group, and of these, not more than 3 may be under 1 year at any one time (Early Years Register, compulsory part of the Childcare Register)" EY337779
But in that situation there are two assistants.
Also found:
"when working with another childminder and an assistant at the above premises, may care for a total of no more than 16 children under 8 years; of these, not more than 8 may be in the early years age group, and of these, not more than 3 may be under 1 year at any one time (Early Years Register, compulsory part of the Childcare Register)" EY344848
So they grant 3 under 1 but it will depend on the number of adults and the registration type of those adults (childminder or assistant).
Oh and they will also grant 4 under 1...
"when working with another childminder and an assistant at the above premises, may care for a total of no more than 11 children under 8 years; of these, not more than 9 may be in the early years age group, and of these, not more than 4 may be under 1 year at any one time (Early Years Register, compulsory part of the Childcare Register)" EY403258
Again that is when the childminder is working with another childminder plus an assistant, so there are 3 adults present.
Google must like Ofsted's new website layout as it has indexed loads of these Childminder Registration Conditions.
It gets better... they will do 5:
"when working with another childminder and an assistant at the above premises, may care for a total of no more than 14 children under 8 years; of these, not more than 7 may be in the early years age group, and of these, not more than 5 may be under 1 year at any one time (Early Years Register, compulsory part of the Childcare Register)" - EY394130
Can't find 6 under 1 though, unless it's a nursery.
In all those cases there were 3 adults present... either childminder+childminder+assistant, or childminder+assistant+assistant.