Gdal image georeferencing and gdal2tiles image flip question

I’m georeferencing an image using gdal and the following command:

gdal_translate -of Gtiff -co tfw=yes -a_ullr 0.016264915466308594 51.505109712517786 -0.0024890899658203125 51.492018739579336 -a_srs EPSG:4326 Penguins.jpg penguins.tif

then I’m generating the tiles using gdal2tiles and the following command:

python gdal2tiles.py -t 'Penguins' -k penguins.tif penguins_gdal

but for some reason the resulting tiles show the image flipped on the y axis even though the tif image is not flipped.

Am I doing something wrong?

Thanks