Temporary babysitter for one month - 3 days a week, 6hrs per day

Looking for an energetic nanny/babysitter to look after my two nephews who are visiting for a month from Greece (20th of june to 18th of july). Requirement is three days per week, 6hrs per day - the days and times can be flexible. Duties will include: staying at home and keeping kids engaged in play indoors and outdoors; taking them to playgrounds; accompanying them with their mum to museus and other trips in London. iDEALLY GREEK SPEAKING