Put the limes in a saucepan and cover with water. Place a small heatproof plate on top of the fruit to keep them submerged and then bring to a boil over a medium heat and simmer for 20-30 mins until the limes are tender. Scoop out the limes, pat them dry with kitchen paper, and discard the cooking water.

Once the limes are cool enough to handle, chop them (peel and pith included) into 3cm chunks and tip everything, including any juice, into a mixing bowl. Stir in the chopped garlic, chilli powder, turmeric and salt, and leave to one side for 1 hour.

Heat a sturdy and dry frying pan over a medium-low heat, and add the mustard seeds, fenugreek, cumin and star anise, Stir and toast the spices for about 40 seconds until aromatic. Tip them into a mortar, add 1 teaspoon of sugar and pound to a powder with a pestle – you can also use an electric spice grinder for this, too.

Add this ground spice mix to the limes, stir well, spoon everything into a sterilised jar and then seal. Leave the pickle in a warm place or on a sunny window ledge for 2-3 days so that flavours mature. Stir the limes once a day with a metal spoon to ensure they are evenly coated in the spice mix.

Heat the oil in a wok or karahi over a medium-high heat and fry the ginger and green chillies for 2-3 mins, until the ginger starts to turn golden. Add the vinegar and sugar and simmer over a medium-low heat until the sugar has dissolved, then boil for 2 mins.

Turn the heat off and add the steeped limes and masala. Leave on one side to cool and then spoon the pickle back into the same jar. Using a metal spoon, push the limes down into the jar so that they are covered by the spicy oil – you might need to add a little extra oil. Seal the jar and leave the pickle for 3-4 days before tasting. It will keep for 3 months at room temperature.