Hi VM,
Nope, as the
British Hallmarks page shows, the Britannia mark is example "B".

British hallmarks come in sets, the rule of thumb is, if you do not have a complete set including:
Standard mark, city mark, date letter and maker's mark (+ a duty mark if 1785-1890), the item is either from another country or more often, as in this case, a piece of silverplate. If your lion in profile mark was on a piece of Britannia, it would be only in conjunction with the Britannia standard mark and the other required marks.
There are a few exceptions, such as on very small items or the odd piece of jewelry.
For comparison, here is an example of a proper set of British hallmarks,

you can see how different they are from the trademarks on your piece.
Regards, Tom